U.S. patent application number 12/661419 was filed with the patent office on 2011-08-18 for apparatus and method for measuring optical characteristics of an object.
Invention is credited to Russell W. Jung, Wayne D. Jung, Alan R. Loudermilk.
Application Number | 20110199606 12/661419 |
Document ID | / |
Family ID | 22734005 |
Filed Date | 2011-08-18 |
United States Patent
Application |
20110199606 |
Kind Code |
A1 |
Jung; Wayne D. ; et
al. |
August 18, 2011 |
Apparatus and method for measuring optical characteristics of an
object
Abstract
Optical characteristic measuring systems and methods such as for
determining the color or other optical characteristics of teeth are
disclosed. Perimeter receiver fiber optics preferably are spaced
apart from a source fiber optic and receive light from the surface
of the object/tooth being measured. Light from the perimeter fiber
optics pass to a variety of filters. The system utilizes the
perimeter receiver fiber optics to determine information regarding
the height and angle of the probe with respect to the object/tooth
being measured. Under processor control, the optical
characteristics measurement may be made at a predetermined height
and angle. Various color spectral photometer arrangements are
disclosed. Translucency, fluorescence, gloss and/or surface texture
data also may be obtained. Audio feedback may be provided to guide
operator use of the system. The probe may have a removable or
shielded tip for contamination prevention. A method of producing
dental prostheses based on measured data also is disclosed.
Measured data also may be stored and/or organized as part of a
patient data base. Such methods and implements may be desirably
utilized for purposes of detecting and preventing counterfeiting or
the like.
Inventors: |
Jung; Wayne D.; (Morton
Grove, IL) ; Jung; Russell W.; (Morton Grove, IL)
; Loudermilk; Alan R.; (Chicago, IL) |
Family ID: |
22734005 |
Appl. No.: |
12/661419 |
Filed: |
March 15, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12218978 |
Jul 18, 2008 |
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12661419 |
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11085934 |
Mar 21, 2005 |
7403285 |
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12218978 |
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10215726 |
Aug 8, 2002 |
6870616 |
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11085934 |
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09198591 |
Nov 23, 1998 |
6449041 |
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10215726 |
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PCT/US98/13764 |
Jun 30, 1998 |
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09198591 |
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PCT/US98/13765 |
Jun 30, 1998 |
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PCT/US98/13764 |
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08886566 |
Jul 1, 1997 |
5966205 |
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PCT/US98/13765 |
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09113033 |
Jul 9, 1998 |
6118521 |
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08886566 |
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Current U.S.
Class: |
356/73 |
Current CPC
Class: |
G01J 3/0278 20130101;
G01J 3/508 20130101; G01N 21/57 20130101; G01J 3/0259 20130101;
G01J 3/0283 20130101; G01J 1/06 20130101; G01J 3/0218 20130101;
G01J 3/0227 20130101; G01J 3/0229 20130101; G01J 3/0251 20130101;
G01J 3/02 20130101; G01J 1/0411 20130101; A61B 2562/247 20130101;
G01J 1/0437 20130101; G01J 3/0264 20130101; G01N 21/474 20130101;
G01J 1/04 20130101; A61C 19/10 20130101; G01J 1/0474 20130101; G01J
3/0205 20130101; A61B 5/0088 20130101; G01J 3/0216 20130101; G01J
3/513 20130101; G01J 3/0208 20130101; A61B 2560/0233 20130101; G01J
3/10 20130101; G07D 7/17 20170501; G01J 3/51 20130101; G01J 3/0291
20130101; G07D 7/1205 20170501 |
Class at
Publication: |
356/73 |
International
Class: |
G01N 21/00 20060101
G01N021/00 |
Claims
1. A method comprising the steps of: moving a probe in proximity to
an object, wherein the probe provides light to a surface of the
object and receives light from the object, wherein light is
provided from the probe by a light source and light is received by
one or more light receivers, wherein the light source and each of
the one or more light receivers define a critical height from the
surface below which no specularly reflected light from the light
source is received by the one or more light receivers; determining
the intensity of light received by the one or more light receivers;
measuring the optical characteristics of the object, wherein the
measurement produces data indicative of the optical characteristics
of the object; and determining data indicative of whether a cable
coupled between the probe and a unit for measuring the optical
characteristics is under a condition of flex, wherein the data
indicative of the optical characteristics of the object is adjusted
based on the determined data.
Description
[0001] This application is a continuation of U.S. application Ser.
No. 11/085,934, filed Mar. 21, 2005, now U.S. Pat. No. 7,403,285,
which is a continuation of U.S. application Ser. No. 10/215,726,
filed on Aug. 8, 2002, now U.S. Pat. No. 6,870,616, which is a
continuation of U.S. application Ser. No. 09/198,591, filed Nov.
23, 1998, now U.S. Pat. No. 6,449,041, which is a
continuation-in-part of the following applications: (1) PCT
Application No. PCT/US98/13764, filed on Jun. 30, 1998, for
Apparatus and Method for Measuring Optical Characteristics of an
Object; (2) PCT Application No. PCT/US98/13765, filed on Jun. 30,
1998, for Apparatus and Method for Measuring Optical
Characteristics of Teeth; (3) U.S. application Ser. No. 08/886,566,
filed on Jul. 1, 1997, for Method and Apparatus for Detecting and
Preventing Counterfeiting, which is now U.S. Pat. No. 5,966,205;
and (4) U.S. application Ser. No. 09/113,033, filed Jul. 9, 1998,
for Method and Apparatus for Measuring Optical Characteristics of
an Object, which is now U.S. Pat. No. 6,118,521.
FIELD OF THE INVENTION
[0002] The present invention relates to devices and methods for
measuring optical characteristics such as color spectrums,
translucence, gloss, and other characteristics of objects such as
teeth, and more particularly to devices and methods for measuring
the color and other optical characteristics of teeth, fabric or
numerous other objects, materials or surfaces with a hand-held
probe that presents minimal problems with height or angular
dependencies and that may be applied to detecting and preventing
counterfeiting.
BACKGROUND OF THE INVENTION
[0003] A need has been recognized for devices and methods of
measuring the color or other optical characteristics of teeth and
other objects in the field of dentistry. There is also a need for
devices and methods for detecting and preventing counterfeiting and
the like based on measurements of various optical characteristics
or properties of objects and materials. Various color measuring
devices such as spectrophotometers and colorimeters are known in
the art. To understand the limitations of such conventional
devices, it is helpful to understand certain principles relating to
color. Without being bound by theory, Applicants provide the
following discussion. In the discussion herein, reference is made
to an "object," "material," "surface," etc., and it should be
understood that in general such discussion may include teeth as
well as other objects or materials as the "object," "material,"
"surface," etc.
[0004] The color of an object determines the manner in which light
is reflected from the object. When light is incident upon an
object, the reflected light will vary in intensity and wavelength
dependent upon the color of the object. Thus, a red object will
reflect red light with a greater intensity than a blue or a green
object, and correspondingly a green object will reflect green light
with a greater intensity than a red or blue object.
[0005] The optical properties of an object are also affected by the
manner in which light is reflected from the surface. Glossy
objects, those that reflect light specularly such as mirrors or
other highly polished surfaces, reflect light differently than
diffuse objects or those that reflect light in all directions, such
as the reflection from a rough or otherwise non-polished surface.
Although both objects may have the same color and exhibit the same
reflectance or absorption optical spectral responses, their
appearances differ because of the manner in which they reflect
light.
[0006] Additionally, many objects may be translucent or have
semi-translucent surfaces or thin layers covering their surfaces.
Examples of such materials are teeth, which have a complicated
structure consisting of an outer enamel layer and an inner dentin
layer. The outer enamel layer is semitranslucent. The inner layers
are also translucent to a greater or lesser degree. Such materials
and objects also appear different from objects that are opaque,
even though they may be the same color because of the manner in
which they can propagate light in the translucent layer and emit
the light ray displaced from its point of entry.
[0007] One method of quantifying the color of an object is to
illuminate it with broad band spectrum or "white" light, and
measure the spectral properties of the reflected light over the
entire visible spectrum and compare the reflected spectrum with the
incident light spectrum. Such instruments typically require a broad
band spectrophotometer, which generally are expensive, bulky and
relatively cumbersome to operate, thereby limiting the practical
application of such instruments.
[0008] For certain applications, the broad band data provided by a
spectrophotometer is unnecessary. For such applications, devices
have been produced or proposed that quantify color in terms of a
numerical value or relatively small set of values representative of
the color of the object.
[0009] It is known that the color of an object can be represented
by three values. For example, the color of an object can be
represented by red, green and blue values, an intensity value and
color difference values, by a CIE value, or by what are known as
"tristimulus values" or numerous other orthogonal combinations. For
most tristimulus systems, the three values are orthogonal; i.e.,
any combination of two elements in the set cannot be included in
the third element.
[0010] One such method of quantifying the color of an object is to
illuminate an object with broad band "white" light and measure the
intensity of the reflected light after it has been passed through
narrow band filters. Typically three filters (such as red, green
and blue) are used to provide tristimulus light values
representative of the color of the surface. Yet another method is
to illuminate an object with three monochromatic light sources or
narrow band light sources (such as red, green and blue) one at a
time and then measure the intensity of the reflected light with a
single light sensor. The three measurements are then converted to a
tristimulus value representative of the color of the surface. Such
color measurement techniques can be utilized to produce equivalent
tristimulus values representative of the color of the surface.
Generally, it does not matter if a "white" light source is used
with a plurality of color sensors (or a continuum in the case of a
spectrophotometer), or if a plurality of colored light sources are
utilized with a single light sensor.
[0011] There are, however, difficulties with the conventional
techniques. When light is incident upon a surface and reflected to
a light receiver, the height of the light sensor and the angle of
the sensor relative to the surface and to the light source also
affect the intensity of the received light. Since the color
determination is being made by measuring and quantifying the
intensity of the received light for different colors, it is
important that the height and angular dependency of the light
receiver be eliminated or accounted for in some manner.
[0012] One method for eliminating the height and angular dependency
of the light source and receiver is to provide a fixed mounting
arrangement where the light source and receiver are stationary and
the object is always positioned and measured at a preset height and
angle. The fixed mounting arrangement greatly limits the
applicability of such a method. Another method is to add mounting
feet to the light source and receiver probe and to touch the object
with the probe to maintain a constant height and angle. The feet in
such an apparatus must be wide enough apart to insure that a
constant angle (usually perpendicular) is maintained relative to
the object. Such an apparatus tends to be very difficult to utilize
on small objects or on objects that are hard to reach, and in
general does not work satisfactorily in measuring objects with
curved surfaces. Such devices are particularly difficult to
implement in the field of dentistry.
[0013] The use of color measuring devices in the field of dentistry
has been proposed. In modern dentistry, the color of teeth
typically are quantified by manually comparing a patient's teeth
with a set of "shade guides." There are numerous shade guides
available for dentists in order to properly select the desired
color of dental prosthesis. Such shade guides have been utilized
for decades and the color determination is made subjectively by the
dentist by holding a set of shade guides next to a patient's teeth
and attempting to find the best match. Unfortunately, however, the
best match often is affected by the ambient light color in the
dental operatory and the surrounding color of the patient's makeup
or clothing and by the fatigue level of the dentist. In addition,
such pseudo trial and error methods based on subjective matching
with existing industry shade guides for forming dental prostheses,
fillings and the like often result in unacceptable color matching,
with the result that the prosthesis needs to be remade, leading to
increased costs and inconvenience to the patient, dental
professional and/or prosthesis manufacturer.
[0014] Similar subjective color quantification also is made in the
paint industry by comparing the color of an object with a paint
reference guide. There are numerous paint guides available in the
industry and the color determination also often is affected by
ambient light color, user fatigue and the color sensitivity of the
user. Many individuals are color insensitive (color blind) to
certain colors, further complicating color determination.
[0015] In general, color quantification is needed in many
industries. Several, but certainly not all, applications include:
dentistry (color of teeth); dermatology (color of skin lesions);
interior decorating (color of paint, fabrics); the textile
industry; automotive repair (matching paint colors); photography
(color of reproductions, color reference of photographs to the
object being photographed); printing and lithography; cosmetics
(hair and skin color, makeup matching); and other applications in
which it useful to measure color in an expedient and reliable
manner.
[0016] While a need has been recognized in the field of dentistry,
however, the limitations of conventional color/optical measuring
techniques typically restrict the utility of such techniques. For
example, the high cost and bulkiness of typical broad band
spectrometers, and the fixed mounting arrangements or feet required
to address the height and angular dependency, often limit the
applicability of such conventional techniques.
[0017] Moreover, another limitation of such conventional methods
and devices are that the resolution of the height and angular
dependency problems typically require contact with the object being
measured. In certain applications, it may be desirable to measure
and quantify the color of an object with a small probe that does
not require contact with the surface of the object. In certain
applications, for example, hygienic considerations make such
contact undesirable. In the other applications such as interior
decorating, contact with the object can mar the surface (such as if
the object is coated in some manner) or otherwise cause undesirable
effects.
[0018] In summary, there is a need for a low cost, hand-held probe
of small size that can reliably measure and quantify the color and
other optical characteristics of an object without requiring
physical contact with the object, and also a need for methods based
on such a device in the field of dentistry and other
applications.
SUMMARY OF THE INVENTION
[0019] In accordance with the present invention, devices and
methods are provided for measuring the color and other optical
characteristics of objects such as teeth, reliably and with minimal
problems of height and angular dependence and which may be applied
to detecting or preventing counterfeiting or the like. A handheld
probe is utilized in the present invention, with the handheld probe
containing a number of fiber optics in certain preferred
embodiments. Light is directed from one (or more) light source(s)
towards the object/tooth to be measured, which in certain preferred
embodiments is a central light source fiber optic (other light
sources and light source arrangements also may be utilized). Light
reflected from the object is detected by a number of light
receivers. Included in the light receivers (which may be light
receiver fiber optics) are a plurality of perimeter and/or
broadband or other receivers (which may be light receiver fiber
optics, etc.). In certain preferred embodiments, a number of groups
of perimeter fiber optics are utilized in order to take
measurements at a desired, and predetermined height and angle,
thereby minimizing height and angular dependency problems found in
conventional methods, and to quantify other optical characteristics
such as gloss. In certain embodiments, the present invention also
may measure gloss, translucence and fluorescence characteristics of
the object/tooth being measured, as well as surface texture and/or
other optical or surface characteristics. In certain embodiments,
the present invention may distinguish the surface spectral
reflectance response and also a bulk spectral response.
[0020] The present invention may include constituent elements of a
broad band spectrophotometer, or, alternatively, may include
constituent elements of a tristimulus type colorimeter. The present
invention may employ a variety of color measuring devices in order
to measure color and other optical characteristics in a practical,
reliable and efficient manner, and in certain preferred embodiments
includes a color filter array and a plurality of color sensors. A
microprocessor is included for control and calculation purposes. A
temperature sensor is included to measure temperature in order to
detect abnormal conditions and/or to compensate for temperature
effects of the filters or other components of the system. In
addition, the present invention may include audio feedback to guide
the operator in making color/optical measurements, as well as one
or more display devices for displaying control, status or other
information.
[0021] With the present invention, color/optical measurements of
teeth or the like may be made with a handheld probe in a practical
and reliable manner, essentially free of height and angular
dependency problems, without resorting to fixtures, feet or other
undesirable mechanical arrangements for fixing the height and angle
of the probe with respect to the object/tooth. In addition, the
present invention includes methods of using such color measurement
data to implement processes for forming dental prostheses and the
like, as well as methods for keeping such color and/or other data
as part of a patient record database.
[0022] Accordingly, it is an object of the present invention to
address limitations of conventional color/optical measuring
techniques.
[0023] It is another object of the present invention to provide a
method and device useful in measuring the color or other optical
characteristics of teeth, fabric or other objects or surfaces with
a hand-held probe of practical size that may advantageously
utilize, but does not necessarily require, contact with the object
or surface.
[0024] It is a further object of the present invention to provide a
color/optical measurement probe and method that does not require
fixed position mechanical mounting, feet or other mechanical
impediments.
[0025] It is yet another object of the present invention to provide
a probe and method useful for measuring color and/or other optical
characteristics that may be utilized with a probe simply placed
near the surface to be measured.
[0026] It is a still further object of the present invention to
provide a probe and method that are capable of determining
translucency characteristics of the object being measured.
[0027] It is a still further object of the present invention to
provide a probe and method that are capable of determining
translucency characteristics of the object being measured by making
measurements from one side of the object.
[0028] It is a further object of the present invention to provide a
probe and method that are capable of determining surface texture
characteristics of the object/tooth being measured.
[0029] It is a still further object of the present invention to
provide a probe and method that are capable of determining
fluorescence characteristics of the object/tooth being
measured.
[0030] It is yet a further object of the present invention to
provide a probe and method that are capable of determining gloss
(or degree of specular reflectance) characteristics of the
object/tooth being measured.
[0031] It is another object of the present invention to provide a
probe and method that can measure the area of a small spot
singularly, or that also can measure the color of irregular shapes
by moving the probe over an area and integrating the color of the
entire area.
[0032] It is a further object of the present invention to provide a
method of measuring the color of teeth and preparing dental
prostheses, dentures, intraoral tooth-colored fillings or other
materials.
[0033] It is yet another object of the present invention to provide
a method and apparatus that minimizes contamination problems, while
providing a reliable and expedient manner in which to measure teeth
and prepare dental prostheses, dentures, intraoral tooth-colored
fillings or other materials.
[0034] It is an object of the present invention to provide methods
of using measured data to implement processes for forming dental
prostheses and the like, as well as methods for keeping such
measurement and/or other data as part of a patient record
database.
[0035] It also is an object of the present invention to provide
probes and methods for measuring optical characteristics with a
probe that is held substantially stationary with respect to the
object or tooth being measured.
[0036] It is another object the present invention to provide
probes, equipment and methods for detecting and preventing
counterfeiting or the like by way of measuring or assessing surface
or subsurface optical characteristics or features.
[0037] Finally, it is an object of the present invention to provide
probes and methods for measuring optical characteristics with a
probe that may have a removable tip or shield that may be removed
for cleaning, disposed after use or the like.
BRIEF DESCRIPTION OF THE DRAWINGS
[0038] The present invention may be more fully understood by a
description of certain preferred embodiments in conjunction with
the attached drawings in which:
[0039] FIG. 1 is a diagram illustrating a preferred embodiment of
the present invention;
[0040] FIG. 2 is a diagram illustrating a cross section of a probe
that may be used in accordance with certain embodiments of the
present invention;
[0041] FIG. 3 is a diagram illustrating an illustrative arrangement
of fiber optic receivers and sensors utilized with certain
embodiments;
[0042] FIGS. 4A to 4C illustrate certain geometric considerations
of fiber optics;
[0043] FIGS. 5A and 5B illustrate the light amplitude received by
fiber optic light receivers as the receivers are moved towards and
away from an object;
[0044] FIG. 6 is a flow chart illustrating a color measuring method
in accordance with an embodiment of the present invention;
[0045] FIGS. 7A and 7B illustrate a protective cap that may be used
with certain embodiments of the present invention;
[0046] FIGS. 8A and 8B illustrate removable probe tips that may be
used with certain embodiments of the present invention;
[0047] FIG. 9 illustrates a fiber optic bundle in accordance with
another embodiment, which may serve to further the understanding of
preferred embodiments of the present invention;
[0048] FIGS. 10A, 10B, 10C and 10D illustrate and describe other
fiber optic bundle configurations and principles, which may serve
to further the understanding of preferred embodiments of the
present invention;
[0049] FIG. 11 illustrates a linear optical sensor array that may
be used in certain embodiments of the present invention;
[0050] FIG. 12 illustrates a matrix optical sensor array that may
be used in certain embodiments of the present invention;
[0051] FIGS. 13A and 13B illustrate certain optical properties of a
filter array that may be used in certain embodiments of the present
invention;
[0052] FIGS. 14A and 14B illustrate examples of received light
intensities of receivers used in certain embodiments of the present
invention;
[0053] FIG. 15 is a flow chart illustrating audio tones that may be
used in certain preferred embodiments of the present invention;
[0054] FIGS. 16A and 16B are flow charts illustrating dental
prosthesis manufacturing methods in accordance with certain
preferred embodiments of the present invention;
[0055] FIGS. 17A and 17B illustrate a positioning implement used in
certain embodiments of the present invention;
[0056] FIG. 18 is a flow chart illustrating a patient database
method in accordance with certain embodiments of the present
invention;
[0057] FIG. 19 illustrates an integrated unit in accordance with
the present invention that includes a measuring device and other
implements;
[0058] FIG. 20 illustrates an embodiment, which utilizes a
plurality of rings of light receivers that may be utilized to take
measurements with the probe held substantially stationary with
respect to the object being measured, which may serve to further
the understanding of preferred embodiments of the present
invention;
[0059] FIGS. 21 and 22 illustrate an embodiment, which utilizes a
mechanical movement and also may be utilized to take measurements
with the probe held substantially stationary with respect to the
object being measured, which may serve to further the understanding
of preferred embodiments of the present invention;
[0060] FIGS. 23A to 23C illustrate embodiments of the present
invention in which coherent light conduits may serve as removable
probe tips;
[0061] FIGS. 24, 25 and 26 illustrate further embodiments of the
present invention utilizing intraoral reflectometers, intraoral
cameras and/or color calibration charts in accordance with the
present invention;
[0062] FIG. 27 illustrates an embodiment of the present invention
in which an interoral camera and/or other instruments in accordance
with the present invention may be adapted for use with a dental
chair;
[0063] FIGS. 28A and 28B illustrate cross sections of probes that
may be used in accordance with preferred embodiments of the present
invention;
[0064] FIGS. 29 and 30A and 30B illustrate certain geometric and
other properties of fiber optics for purposes of understanding
certain preferred embodiments;
[0065] FIGS. 31A and 31B illustrate probes for measuring
"specular-excluded" type spectrums in accordance with the present
invention;
[0066] FIGS. 32, 33 and 34 illustrate embodiments in which intra
oral cameras and reflectometer type instruments in accordance with
the present invention are integrated;
[0067] FIGS. 35 and 36 illustrate certain handheld embodiments of
the present invention;
[0068] FIGS. 37A and 37B illustrate a tooth dental object in cross
section, illustrating how embodiments of the present invention may
be used to assess subsurface characteristics of various types of
objects;
[0069] FIGS. 38 to 50 illustrate other embodiments (systems,
sources, receivers, etc.), aspects and features within the scope of
the present invention;
[0070] FIGS. 51A to 51C illustrate materials or object portions for
purposes of explaining preferred embodiments of methods and devices
for detecting or preventing counterfeiting or the like;
[0071] FIGS. 52 to 58 illustrate yet other embodiments (systems,
sources, receivers, methods, etc.), aspects and features within the
scope of the present invention, including implements having a
central receiver element and detecting and quantifying flex of a
cable;
[0072] FIG. 59 illustrates an embodiment of the present invention
employing a linear optical sensor;
[0073] FIG. 60 illustrates an embodiment of the present invention
in which light is split and provided to a spectrometer and wideband
sensor(s); and
[0074] FIGS. 61 and 62 illustrate embodiments employing a CCD
sensing element.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0075] The present invention will be described in greater detail
with reference to certain preferred embodiments and certain other
embodiments, which may serve to further the understanding of
preferred embodiments of the present invention. At various places
herein, reference is made to an "object," "material," "surface,"
etc., for example. It should be understood that an exemplary use of
the present invention is in the field of dentistry, and thus the
object typically should be understood to include teeth, dentures or
other prosthesis or restorations, dental-type cements or the like
or other dental objects, although for discussion purposes in
certain instances reference is only made to the "object." As
described elsewhere herein, various refinements and substitutions
of the various embodiments are possible based on the principles and
teachings herein.
[0076] With reference to FIG. 1, an exemplary preferred embodiment
of a color/optical characteristic measuring system and method in
accordance with the present invention will be described. It should
be noted that, at various places herein, such a color measuring
system is sometimes referred to as an intraoral reflectometer,
etc.
[0077] Probe tip 1 encloses a plurality of fiber optics, each of
which may constitute one or more fiber optic fibers. In a preferred
embodiment, the fiber optics contained within probe tip 1 includes
a single light source fiber optic and a number of groups of light
receiver fiber optics. The use of such fiber optics to measure the
color or other optical characteristics of an object will be
described later herein. Probe tip 1 is attached to probe body 2, on
which is fixed switch 17. Switch 17 communicates with
microprocessor 10 through wire 18 and provides, for example, a
mechanism by which an operator may activate the device in order to
make a color/optical measurement. Fiber optics within probe tip 1
terminate at the forward end thereof (i.e., the end away from probe
body 2). The forward end of probe tip 1 is directed towards the
surface of the object to be measured as described more fully below.
The fiber optics within probe tip 1 optically extend through probe
body 2 and through fiber optic cable 3 to light sensors 8, which
are coupled to microprocessor 10.
[0078] It should be noted that microprocessor 10 includes
conventional associated components, such as memory (programmable
memory, such as PROM, EPROM or EEPROM; working memory such as DRAMs
or SRAMs; and/or other types of memory such as non-volatile memory,
such as FLASH), peripheral circuits, clocks and power supplies,
although for clarity such components are not explicitly shown.
Other types of computing devices (such as other microprocessor
systems, programmable logic arrays or the like) are used in other
embodiments of the present invention.
[0079] In the embodiment of FIG. 1, the fiber optics from fiber
optic cable 3 end at splicing connector 4. From splicing connector
4, each or some of the receiver fiber optics used in this
embodiment is/are spliced into a number of smaller fiber optics
(generally denoted as fibers 7), which in this embodiment are
fibers of equal diameter, but which in other preferred embodiments
may be of unequal diameter and/or numeric aperture (NA) (including,
for example, larger or smaller "height/angle" or perimeter fibers,
as more fully described herein). One of the fibers of each group of
fibers may pass to light sensors 8 through a neutral density filter
(as more fully described with reference to FIG. 3), and
collectively such neutrally filtered fibers may be utilized for
purposes of height/angle determination, translucency determination
and gloss determination (and also may be utilized to measure other
surface characteristics, as more fully described herein). Remaining
fibers of each group of fibers may pass to light sensors 8 through
color filters and may be used to make color/optical measurements.
In still other embodiments, splicing connector 4 is not used, and
fiber bundles of, for example, five or more fibers each extend from
light sensors 8 to the forward end of probe tip 1. In certain
embodiments, unused fibers or other materials may be included as
part of a bundle of fibers for purposes of, for example, easing the
manufacturing process for the fiber bundle. What should be noted is
that, for purposes of the present invention, a plurality of light
receiver fiber optics or elements (such as fibers 7) are presented
to light sensors 8, with the light from the light receiver fiber
optics/elements representing light reflected from object 20. While
the various embodiments described herein present tradeoffs and
benefits that may not have been apparent prior to the present
invention (and thus may be independently novel), what is important
for the present discussion is that light from fiber optics/elements
at the forward end of probe tip 1 is presented to sensors 8 for
color/optical measurements and angle/height determination, etc. In
particular, fiber optic configurations of certain preferred
embodiments will be explained in more detail hereinafter.
[0080] Light source 11 in the preferred embodiment is a halogen
light source (of, for example, 5-100 watts, with the particular
wattage chosen for the particular application), which may be under
the control of microprocessor 10. The light from light source 11
reflects from cold mirror 6 and into source fiber optic 5. Source
fiber optic 5 passes through to the forward end of probe tip 1 and
provides the light stimulus used for purposes of making the
measurements described herein. Cold mirror 6 reflects visible light
and passes infra-red light, and is used to reduce the amount of
infra-red light produced by light source 11 before the light is
introduced into source fiber optic 5. Such infra-red light
reduction of the light from a halogen source such as light source
11 can help prevent saturation of the receiving light sensors,
which can reduce overall system sensitivity. Fiber 15 receives
light directly from light source 11 and passes through to light
sensors 8 (which may be through a neutral density filter).
Microprocessor 10 monitors the light output of light source 11
through fiber 15, and thus may monitor and, if necessary compensate
for, drift of the output of light source 11. In certain
embodiments, microprocessor 10 also may sound an alarm (such as
through speaker 16) or otherwise provide some indication if
abnormal or other undesired performance of light source 11 is
detected.
[0081] The data output from light sensors 8 pass to microprocessor
10. Microprocessor 10 processes the data from light sensors 8 to
produce a measurement of color and/or other characteristics.
Microprocessor 10 also is coupled to key pad switches 12, which
serve as an input device. Through key pad switches 12, the operator
may input control information or commands, or information relating
to the object being measured or the like. In general, key pad
switches 12, or other suitable data input devices (such as push
button, toggle, membrane or other switches or the like), serve as a
mechanism to input desired information to microprocessor 10.
[0082] Microprocessor 10 also communicates with UART 13, which
enables microprocessor 10 to be coupled to an external device such
as computer 13A. In such embodiments, data provided by
microprocessor 10 may be processed as desired for the particular
application, such as for averaging, format conversion or for
various display or print options, etc. In the preferred embodiment,
UART 13 is configured so as to provide what is known as a RS232
interface, such as is commonly found in personal computers.
[0083] Microprocessor 10 also communicates with LCD 14 for purposes
of displaying status, control or other information as desired for
the particular application. For example, color bars, charts or
other graphic representations of the color or other collected data
and/or the measured object or tooth may be displayed. In other
embodiments, other display devices are used, such as CRTs,
matrix-type LEDs, lights or other mechanisms for producing a
visible indicia of system status or the like. Upon system
initialization, for example, LCD 14 may provide an indication that
the system is stable, ready and available for taking color
measurements.
[0084] Also coupled to microprocessor 10 is speaker 16. Speaker 16,
in a preferred embodiment as discussed more fully below, serves to
provide audio feedback to the operator, which may serve to guide
the operator in the use of the device. Speaker 16 also may serve to
provide status or other information alerting the operator of the
condition of the system, including an audio tone, beeps or other
audible indication (i.e., voice) that the system is initialized and
available for taking measurements. Speaker 16 also may present
audio information indicative of the measured data, shade guide or
reference values corresponding to the measured data, or an
indication of the status of the color/optical measurements.
[0085] Microprocessor 10 also receives an input from temperature
sensor 9. Given that many types of filters (and perhaps light
sources or other components) may operate reliably only in a given
temperature range, temperature sensor 9 serves to provide
temperature information to microprocessor 10. In particular, color
filters, such as may be included in light sensors 8, may be
sensitive to temperature, and may operate reliably only over a
certain temperature range. In certain embodiments, if the
temperature is within a usable range, microprocessor 10 may
compensate for temperature variations of the color filters. In such
embodiments, the color filters are characterized as to filtering
characteristics as a function of temperature, either by data
provided by the filter manufacturer, or through measurement as a
function of temperature. Such filter temperature compensation data
may be stored in the form of a look-up table in memory, or may be
stored as a set of polynomial coefficients from which the
temperature characteristics of the filters may be computed by
microprocessor 10.
[0086] In general, under control of microprocessor 10, which may be
in response to operator activation (through, for example, key pad
switches 12 or switch 17), light is directed from light source 11,
and reflected from cold mirror 6 through source fiber optic 5 (and
through fiber optic cable 3, probe body 2 and probe tip 1) or
through some other suitable light source element and is directed
onto object 20. Light reflected from object 20 passes through the
receiver fiber optics/elements in probe tip 1 to light sensors 8
(through probe body 2, fiber optic cable 3 and fibers 7). Based on
the information produced by light sensors 8, microprocessor 10
produces a color/optical measurement result or other information to
the operator. Color measurement or other data produced by
microprocessor 10 may be displayed on display 14, passed through
UART 13 to computer 13A, or used to generate audio information that
is presented to speaker 16. Other operational aspects of the
preferred embodiment illustrated in FIG. 1 will be explained
hereinafter.
[0087] With reference to FIG. 2, an embodiment of a fiber optic
arrangement presented at the forward end of probe tip 1 will now be
described, which may serve to further the understanding of
preferred embodiments of the present invention. As illustrated in
FIG. 2, this embodiment utilizes a single central light source
fiber optic, denoted as light source fiber optic S, and a plurality
of perimeter light receiver fiber optics, denoted as light
receivers R1, R2 and R3. As is illustrated, this embodiment
utilizes three perimeter fiber optics, although in other
embodiments two, four or some other number of receiver fiber optics
are utilized. As more fully described herein, the perimeter light
receiver fiber optics serve not only to provide reflected light for
purposes of making the color/optical measurement, but such
perimeter fibers also serve to provide information regarding the
angle and height of probe tip 1 with respect to the surface of the
object that is being measured, and also may provide information
regarding the surface characteristics of the object that is being
measured.
[0088] In the illustrated embodiment, receiver fiber optics R1 to
R3 are positioned symmetrically around source fiber optic S, with a
spacing of about 120 degrees from each other. It should be noted
that spacing t is provided between receiver fiber optics R1 to R3
and source fiber optic S. While the precise angular placement of
the receiver fiber optics around the perimeter of the fiber bundle
in general is not critical, it has been determined that three
receiver fiber optics positioned 120 degrees apart generally may
give acceptable results. As discussed above, in certain embodiments
light receiver fiber optics R1 to R3 each constitute a single
fiber, which is divided at splicing connector 4 (refer again to
FIG. 1), or, in alternate embodiments, light receiver fiber optics
R1 to R3 each constitute a bundle of fibers, numbering, for
example, at least five fibers per bundle. It has been determined
that, with available fibers of uniform size, a bundle of, for
example, seven fibers may be readily produced (although as will be
apparent to one of skill in the art, the precise number of fibers
may be determined in view of the desired number of receiver fiber
optics, manufacturing considerations, etc.). The use of light
receiver fiber optics R1 to R3 to produce color/optical
measurements is further described elsewhere herein, although it may
be noted here that receiver fiber optics R1 to R3 may serve to
detect whether, for example, the angle of probe tip 1 with respect
to the surface of the object being measured is at 90 degrees, or if
the surface of the object being measured contains surface texture
and/or spectral irregularities. In the case where probe tip 1 is
perpendicular to the surface of the object being measured and the
surface of the object being measured is a diffuse reflector (i.e.,
a matte-type reflector, as compared to a glossy or spectral or
shiny-type reflector which may have "hot spots"), then the light
intensity input into the perimeter fibers should be approximately
equal. It also should be noted that spacing t serves to adjust the
optimal height at which color/optical measurements should be made
(as more fully described below). Preferred embodiments, as
described hereinafter, may enable the quantification of the gloss
or degree of spectral reflection of the object being measured.
[0089] In one particular aspect useful with embodiments of the
present invention, area between the fiber optics on probe tip 1 may
be wholly or partially filled with a non-reflective material and/or
surface (which may be a black mat, contoured or other
non-reflective surface). Having such exposed area of probe tip 1
non-reflective helps to reduce undesired reflections, thereby
helping to increase the accuracy and reliability.
[0090] With reference to FIG. 3, a partial arrangement of light
receiver fiber optics and sensors that may be used in a preferred
embodiment of the present invention will now be described. Fibers 7
represent light receiving fiber optics, which transmit light
reflected from the object being measured to light sensors 8. In an
exemplary embodiment, sixteen sensors (two sets of eight) are
utilized, although for ease of discussion only 8 are illustrated in
FIG. 3 (in this preferred embodiment, the circuitry of FIG. 3 is
duplicated, for example, in order to result in sixteen sensors). In
other embodiments, other numbers of sensors are utilized in
accordance with the present invention.
[0091] Light from fibers 7 is presented to sensors 8, which in a
preferred embodiment pass through filters 22 to sensing elements
24. In this preferred embodiment, sensing elements 24 include
light-to-frequency converters, manufactured by Texas Instruments
and sold under the part number TSL230. Such converters constitute,
in general, photo diode arrays that integrate the light received
from fibers 7 and output an AC signal with a frequency proportional
to the intensity (not frequency) of the incident light. Without
being bound by theory, the basic principle of such devices is that,
as the intensity increases, the integrator output voltage rises
more quickly, and the shorter the integrator rise time, the greater
the output frequency. The outputs of the TSL230 sensors are TTL
compatible digital signals, which may be coupled to various digital
logic devices.
[0092] The outputs of sensing elements 24 are, in this embodiment,
asynchronous signals of frequencies depending upon the light
intensity presented to the particular sensing elements, which are
presented to processor 26. In a preferred embodiment, processor 26
is a Microchip PIC16C55 or PIC16C57 microprocessor, which as
described more fully herein implements an algorithm to measure the
frequencies of the signals output by sensing elements 24. In other
embodiments, a more integrated microprocessor/microcontroller, such
as Hitachi's SH RISC microcontrollers, is utilized to provide
further system integration or the like.
[0093] As previously described, processor 26 measures the
frequencies of the signals output from sensing elements 24. In a
preferred embodiment, processor 26 implements a software timing
loop, and at periodic intervals processor 26 reads the states of
the outputs of sensing elements 24. An internal counter is
incremented each pass through the software timing loop. The
accuracy of the timing loop generally is determined by the crystal
oscillator time base (not shown in FIG. 3) coupled to processor 26
(such oscillators typically are quite stable). After reading the
outputs of sensing elements 24, processor 26 performs an exclusive
OR ("XOR") operation with the last data read (in a preferred
embodiment such data is read in byte length). If any bit has
changed, the XOR operation will produce a 1, and, if no bits have
changed, the XOR operation will produce a 0. If the result is
non-zero, the input byte is saved along with the value of the
internal counter (that is incremented each pass through the
software timing loop). If the result is zero, the systems waits
(e.g., executes no operation instructions) the same amount of time
as if the data had to be saved, and the looping operation
continues. The process continues until all eight inputs have
changed at least twice, which enables measurement of a full 1/2
period of each input. Upon conclusion of the looping process,
processor 26 analyzes the stored input bytes and internal counter
states. There should be 2 to 16 saved inputs (for the 8 total
sensors of FIG. 3) and counter states (if two or more inputs change
at the same time, they are saved simultaneously). As will be
understood by one of skill in the art, the stored values of the
internal counter contains information determinative of the period
of the signals received from sensing elements 24. By proper
subtraction of internal counter values at times when an input bit
has changed, the period may be calculated. Such periods calculated
for each of the outputs of sensing elements is provided by
processor 26 to microprocessor 10 (see, e.g., FIG. 1). From such
calculated periods, a measure of the received light intensities may
be calculated. In alternate embodiments, the frequency of the
outputs of the TSL230 sensors is measured directly by a similar
software loop as the one described above. The outputs are monitored
by the RISC processor in a software timing loop and are XORed with
the previous input as described above. If a transition occurs for a
particular TSL230 input, a counter register for the particular
TSL230 input is incremented. The software loop is executed for a
pre-determined period of time and the frequency of the input is
calculated by dividing the number of transitions by the
pre-determined time and scaling the result. It will also be
apparent to one skilled in the art that more sophisticated
measurement schemes can also be implemented whereby both the
frequency and period are simultaneously measured by high speed RISC
processors such as those of the Hitachi SH family.
[0094] It should be noted that the sensing circuitry and
methodology illustrated in FIG. 3 have been determined to provide a
practical and expedient manner in which to measure the light
intensities received by sensing elements 24. In other embodiments,
other circuits and methodologies are employed (such other exemplary
sensing schemes are described elsewhere herein).
[0095] As discussed above with reference to FIG. 1, one or more of
fibers 7 measures light source 11, which may be through a neutral
density filter, which serves to reduce the intensity of the
received light in order to maintain the intensity roughly in the
range of the other received light intensities. A number of fibers 7
also are from perimeter receiver fiber optics R1 to R3 (see, e.g.,
FIG. 2) and also may pass through neutral density filters. Such
receiving fibers 7 serve to provide data from which angle/height
information and/or surface characteristics may be determined.
[0096] The remaining twelve fibers (of the illustrated embodiment's
total of 16 fibers) of fibers 7 pass through color filters and are
used to produce the color measurement. In an embodiment, the color
filters are Kodak Sharp Cutting Wratten Gelatin Filters, which pass
light with wavelengths greater than the cut-off value of the filter
(i.e., reddish values), and absorb light with wavelengths less than
the cut-off value of the filter (i.e., bluish values). "Sharp
Cutting" filters are available in a wide variety of cut-off
frequencies/wavelengths, and the cut-off values generally may be
selected by proper selection of the desired cut-off filter. In an
embodiment, the filter cut-off values are chosen to cover the
entire visible spectrum and, in general, to have band spacings of
approximately the visible band range (or other desired range)
divided by the number of receivers/filters. As an example, 700
nanometers minus 400 nanometers, divided by 11 bands (produced by
twelve color receivers/sensors), is roughly 30 nanometer band
spacing.
[0097] With an array of cut-off filters as described above, and
without being bound by theory or the specific embodiments described
herein, the received optical spectrum may be measured/calculated by
subtracting the light intensities of "adjacent" color receivers.
For example, band 1 (400 nm to 430 nm)=(intensity of receiver 12)
minus (intensity of receiver 11), and so on for the remaining
bands. Such an array of cut-off filters, and the intensity values
that may result from filtering with such an array, are more fully
described in connection with FIGS. 13A to 14B.
[0098] It should be noted here that in alternate embodiments other
color filter arrangements are utilized. For example, "notch" or
bandpass filters may be utilized, such as may be developed using
Schott glass-type filters (whether constructed from separate
longpass/shortpass filters or otherwise) or notch interference
filters such as those manufactured by Corion, etc.
[0099] In a preferred embodiment of the present invention, the
specific characteristics of the light source, filters, sensors and
fiber optics, etc., are normalized/calibrated by directing the
probe towards, and measuring, a known color standard. Such
normalization/calibration may be performed by placing the probe in
a suitable fixture, with the probe directed from a predetermined
position (i.e., height and angle) from the known color standard.
Such measured normalization/calibration data may be stored, for
example, in a look-up table, and used by microprocessor 10 to
normalize or correct measured color or other data. Such procedures
may be conducted at start-up, at regular periodic intervals, or by
operator command, etc. In particular embodiments, a large number of
measurements may be taken on materials of particular
characteristics and processed and/or statistically analyzed or the
like, with data representing or derived from such measurements
stored in memory (such as a look-up table or polynomial or other
coefficients, etc.). Thereafter, based upon measurements of an
object taken in accordance with the present invention, comparisons
may be made with the stored data and assessments of the measured
object made or predicted. In one illustrative example, an
assessment or prediction may be made of whether the object is wet
or dry (having water or other liquid on its surface, wet paint,
etc.) based on measurements in accordance with the present
invention. In yet another illustrative example, an assessment or
prediction of the characteristics of an underlying material, such
as the pulpal tissue within a tooth may be made. Such capabilities
may be further enhanced by comparisons with measurements taken of
the object at an earlier time, such as data taken of the tooth or
other object at one or more earlier points in time. Such
comparisons based on such historical data and/or stored data may
allow highly useful assessments or predictions of the current or
projected condition or status of the tooth, tissue or other object,
etc. Many other industrial uses of such surface and subsurface
assessment/prediction capabilities are possible.
[0100] What should be noted from the above description is that the
receiving and sensing fiber optics and circuitry illustrated in
FIG. 3 provide a practical and expedient way to determine the color
and other optical or other characteristics by measuring the
intensity of the light reflected from the surface of the object
being measured.
[0101] It also should be noted that such a system measures the
spectral band of the reflected light from the object, and once
measured such spectral data may be utilized in a variety of ways.
For example, such spectral data may be displayed directly as
intensity-wavelength band values. In addition, tristimulus type
values may be readily computed (through, for example, conventional
matrix math), as may any other desired color values. In one
particular embodiment useful in dental applications (such as for
dental prostheses), the color data is output in the form of a
closest match or matches of dental shade guide value(s). In a
preferred embodiment, various existing shade guides (such as the
shade guides produced by Vita Zahnfabrik) are characterized and
stored in a look-up table, or in the graphics art industry Pantone
color references, and the color measurement data are used to select
the closest shade guide value or values, which may be accompanied
by a confidence level or other suitable factor indicating the
degree of closeness of the match or matches, including, for
example, what are known as .DELTA.E values or ranges of .DELTA.E
values, or criteria based on standard deviations, such as standard
deviation minimization. In still other embodiments, the color
measurement data are used (such as with look-up tables) to select
materials for the composition of paint or ceramics such as for
prosthetic teeth. There are many other uses of such spectral data
measured in accordance with the present invention.
[0102] It is known that certain objects such as human teeth may
fluoresce, and such optical characteristics also may be measured in
accordance with the present invention. A light source with an
ultraviolet component may be used to produce more accurate
color/optical data with respect to such objects. Such data may be
utilized to adjust the amounts and or proportions or types of
dental fluorescing materials in dental restorations or prosthesis.
In certain embodiments, a tungsten/halogen source (such as used in
a preferred embodiment) may be combined with a UV light source
(such as a mercury vapor, xenon or other fluorescent light source,
etc.) to produce a light output capable of causing the object to
fluoresce. Alternately, a separate UV light source, combined with a
visible-light-blocking filter, may be used to illuminate the
object. Such a UV light source may be combined with light from a
red LED (for example) in order to provide a visual indication of
when the UV light is on and also to serve as an aid for the
directional positioning of the probe operating with such a light
source. A second measurement may be taken using the UV light source
in a manner analogous to that described earlier, with the band of
the red LED or other supplemental light source being ignored. The
second measurement may thus be used to produce an indication of the
fluorescence of the tooth or other object being measured. With such
a UV light source, a silica fiber optic (or other suitable
material) typically would be required to transmit the light to the
object (standard fiber optic materials such as glass and plastic in
general do not propagate UV light in a desired manner, etc.).
[0103] As described earlier, in certain preferred embodiments the
present invention utilizes a plurality of perimeter receiver fiber
optics spaced apart from and around a central source fiber optic to
measure color and determine information regarding the height and
angle of the probe with respect to the surface of the object being
measured, which may include other surface characteristic
information, etc. Without being bound by theory, certain principles
underlying certain aspects of the present invention will now be
described with reference to FIGS. 4A to 4C.
[0104] FIG. 4A illustrates a typical step index fiber optic
consisting of a core and a cladding. For this discussion, it is
assumed that the core has an index of refraction of n.sub.0 and the
cladding has an index of refraction of n.sub.1. Although the
following discussion is directed to "step index" fibers, it will be
appreciated by those of skill in the art that such discussion
generally is applicable for gradient index fibers as well.
[0105] In order to propagate light without loss, the light must be
incident within the core of the fiber optic at an angle greater
than the critical angle, which may be represented as Sin.sup.-1
{n.sub.1/n.sub.0}, where no is the index of refraction of the core
and n.sub.1 is the index of refraction of the cladding. Thus, all
light must enter the fiber at an acceptance angle equal to or less
than phi, with phi=2.times.Sin.sup.-1 {
(n.sub.0.sup.2-n.sub.1.sup.2)}, or it will not be propagated in a
desired manner.
[0106] For light entering a fiber optic, it must enter within the
acceptance angle phi. Similarly, when the light exits a fiber
optic, it will exit the fiber optic within a cone of angle phi as
illustrated in FIG. 4A. The value (n.sub.0.sup.2-n.sub.1.sup.2) is
referred to as the aperture of the fiber optic. For example, a
typical fiber optic may have an aperture of 0.5, and an acceptance
angle of 60.degree..
[0107] Consider using a fiber optic as a light source. One end is
illuminated by a light source (such as light source 11 of FIG. 1),
and the other is held near a surface. The fiber optic will emit a
cone of light as illustrated in FIG. 4A. If the fiber optic is held
perpendicular to a surface it will create a circular light pattern
on the surface. As the fiber optic is raised, the radius r of the
circle will increase. As the fiber optic is lowered, the radius of
the light pattern will decrease. Thus, the intensity of the light
(light energy per unit area) in the illuminated circular area will
increase as the fiber optic is lowered and will decrease as the
fiber optic is raised.
[0108] The same principle generally is true for a fiber optic being
utilized as a receiver. Consider mounting a light sensor on one end
of a fiber optic and holding the other end near an illuminated
surface. The fiber optic can only propagate light without loss when
the light entering the fiber optic is incident on the end of the
fiber optic near the surface if the light enters the fiber optic
within its acceptance angle phi. A fiber optic utilized as a light
receiver near a surface will only accept and propagate light from
the circular area of radius r on the surface. As the fiber optic is
raised from the surface, the area increases. As the fiber optic is
lowered to the surface, the area decreases.
[0109] Consider two fiber optics parallel to each other as
illustrated in FIG. 4B. For simplicity of discussion, the two fiber
optics illustrated are identical in size and aperture. The
following discussion, however, generally would be applicable for
fiber optics that differ in size and aperture. One fiber optic is a
source fiber optic, the other fiber optic is a receiver fiber
optic. As the two fiber optics are held perpendicular to a surface,
the source fiber optic emits a cone of light that illuminates a
circular area of radius r. The receiver fiber optic can only accept
light that is within its acceptance angle phi, or only light that
is received within a cone of angle phi. If the only light available
is that emitted by the source fiber optic, then the only light that
can be accepted by the receiver fiber optic is the light that
strikes the surface at the intersection of the two circles as
illustrated in FIG. 4C. As the two fiber optics are lifted from the
surface, the proportion of the intersection of the two circular
areas relative to the circular area of the source fiber optic
increases. As they near the surface, the proportion of the
intersection of the two circular areas to the circular area of the
source fiber optic decreases. If the fiber optics are held too
close to the surface (i.e., at or below a "critical height"
h.sub.c), the circular areas will no longer intersect and no light
emitted from the source fiber optic will be received by the
receiver fiber optic.
[0110] As discussed earlier, the intensity of the light in the
circular area illuminated by the source fiber increases as the
fiber is lowered to the surface. The intersection of the two cones,
however, decreases as the fiber optic pair is lowered. Thus, as the
fiber optic pair is lowered to a surface, the total intensity of
light received by the receiver fiber optic increases to a maximal
value, and then decreases sharply as the fiber optic pair is
lowered still further to the surface. Eventually, the intensity
will decrease essentially to zero at or below the critical height
h.sub.c (assuming the object being measured is not translucent, as
described more fully herein), and will remain essentially zero
until the fiber optic pair is in contact with the surface. Thus, as
a source-receiver pair of fiber optics as described above are
positioned near a surface and as their height is varied, the
intensity of light received by the receiver fiber optic reaches a
maximal value at a peaking or "peaking height" h.sub.p.
[0111] Again without being bound by theory, an interesting property
of the peaking height h.sub.p has been observed. The peaking height
h.sub.p is a function primarily of the geometry of fixed
parameters, such as fiber apertures, fiber diameters and fiber
spacing. Since the receiver fiber optic in the illustrated
arrangement is only detecting a maximum value and not attempting to
quantify the value, its maximum in general is independent of the
surface color. It is only necessary that the surface reflect
sufficient light from the intersecting area of the source and
receiver fiber optics to be within the detection range of the
receiver fiber optic light sensor. Thus, in general red or green or
blue or any color surface will all exhibit a maximum at the same
peaking height h.sub.p.
[0112] Although the above discussion has focused on two fiber
optics perpendicular to a surface, similar analysis is applicable
for fiber optic pairs at other angles. When a fiber optic is not
perpendicular to a surface, it generally illuminates an elliptical
area. Similarly, the acceptance area of a receiver fiber optic
generally becomes elliptical. As the fiber optic pair is moved
closer to the surface, the receiver fiber optic also will detect a
maximal value at a peaking height independent of the surface color
or characteristics. The maximal intensity value measured when the
fiber optic pair is not perpendicular to the surface, however, will
be less than the maximal intensity value measured when the fiber
optic pair is perpendicular to the surface.
[0113] Referring now to FIGS. 5A and 5B, the intensity of light
received as a fiber optic source-receiver pair is moved to and from
a surface will now be described. FIG. 5A illustrates the intensity
of the received light as a function of time. Corresponding FIG. 5B
illustrates the height of the fiber optic pair from the surface of
the object being measured. FIGS. 5A and 5B illustrate (for ease of
discussion) a relatively uniform rate of motion of the fiber optic
pair to and from the surface of the object being measured (although
similar illustrations/analysis would be applicable for non-uniform
rates as well).
[0114] FIG. 5A illustrates the intensity of received light as the
fiber optic pair is moved to and then from a surface. While FIG. 5A
illustrates the intensity relationship for a single receiver fiber
optic, similar intensity relationships would be expected to be
observed for other receiver fiber optics, such as, for example, the
multiple receiver fiber optics of FIGS. 1 and 2. In general with
the preferred embodiment described above, all fifteen fiber optic
receivers (of fibers 7) will exhibit curves similar to that
illustrated in FIG. 5A.
[0115] FIG. 5A illustrates five regions. In region 1, the probe is
moved towards the surface of the object being measured, which
causes the received light intensity to increase. In region 2, the
probe is moved past the peaking height, and the received light
intensity peaks and then falls off sharply. In region 3, the probe
essentially is in contact with the surface of the object being
measured. As illustrated, the received intensity in region 3 will
vary depending upon the translucence of the object being measured.
If the object is opaque, the received light intensity will be very
low, or almost zero (perhaps out of range of the sensing
circuitry). If the object is translucent, however, the light
intensity will be quite high, but in general should be less than
the peak value. In region 4, the probe is lifted and the light
intensity rises sharply to a maximum value. In region 5, the probe
is lifted further away from the object, and the light intensity
decreases again.
[0116] As illustrated, two peak intensity values (discussed as P1
and P2 below) should be detected as the fiber optic pair moves to
and from the object at the peaking height h.sub.p. If peaks P1 and
P2 produced by a receiver fiber optic are the same value, this
generally is an indication that the probe has been moved to and
from the surface of the object to be measured in a consistent
manner. If peaks P1 and P2 are of different values, then these may
be an indication that the probe was not moved to and from the
surface of the object in a desired manner, or that the surface is
curved or textured, as described more fully herein. In such a case,
the data may be considered suspect and rejected. In addition, peaks
P1 and P2 for each of the perimeter fiber optics (see, e.g., FIG.
2) should occur at the same height (assuming the geometric
attributes of the perimeter fiber optics, such as aperture,
diameter and spacing from the source fiber optic, etc.). Thus, the
perimeter fiber optics of a probe moved in a consistent,
perpendicular manner to and from the surface of the object being
measured should have peaks P1 and P2 that occur at the same height.
Monitoring receiver fibers from the perimeter receiver fiber optics
and looking for simultaneous (or near simultaneous, e.g., within a
predetermined range) peaks P1 and P2 provides a mechanism for
determining if the probe is held at a desired perpendicular angle
with respect to the object being measured.
[0117] In addition, the relative intensity level in region 3 serves
as an indication of the level of translucency of the object being
measured. Again, such principles generally are applicable to the
totality of receiver fiber optics in the probe (see, e.g., fibers 7
of FIGS. 1 and 3). Based on such principles, measurement techniques
that may be applicable with respect to embodiments disclosed herein
will now be described.
[0118] FIG. 6 is a flow chart illustrating a general measuring
technique that may be used in accordance with certain embodiments
of the present invention. Step 49 indicates the start or beginning
of a color/optical measurement. During step 49, any equipment
initialization, diagnostic or setup procedures may be performed.
Audio or visual information or other indicia may be given to the
operator to inform the operator that the system is available and
ready to take a measurement. Initiation of the color/optical
measurement commences by the operator moving the probe towards the
object to be measured, and may be accompanied by, for example,
activation of switch 17 (see FIG. 1).
[0119] In step 50, the system on a continuing basis monitors the
intensity levels for the receiver fiber optics (see, e.g., fibers 7
of FIG. 1). If the intensity is rising, step 50 is repeated until a
peak is detected. If a peak is detected, the process proceeds to
step 52. In step 52, measured peak intensity P1, and the time at
which such peak occurred, are stored in memory (such as in memory
included as a part of microprocessor 10), and the process proceeds
to step 54. In step 54, the system continues to monitor the
intensity levels of the receiver fiber optics. If the intensity is
falling, step 54 is repeated. If a "valley" or plateau is detected
(i.e., the intensity is no longer falling, which generally
indicates contact or near contact with the object), then the
process proceeds to step 56. In step 56, the measured surface
intensity (IS) is stored in memory, and the process proceeds to
step 58. In step 58, the system continues to monitor the intensity
levels of the receiver fibers. If the intensity is rising, step 58
is repeated until a peak is detected. If a peak is detected, the
process proceeds to step 60. In step 60, measured peak intensity
P2, and the time at which such peak occurred, are stored in memory,
and the process proceeds to step 62. In step 62, the system
continues to monitor the intensity levels of the receiver fiber
optics. Once the received intensity levels begin to fall from peak
P2, the system perceives that region 5 has been entered (see, e.g.,
FIG. 5A), and the process proceeds to step 64.
[0120] In step 64, the system, under control of microprocessor 10,
may analyze the collected data taken by the sensing circuitry for
the various receiver fiber optics. In step 64, peaks P1 and P2 of
one or more of the various fiber optics may be compared. If any of
peaks P1 and P2 for any of the various receiver fiber optics have
unequal peak values, then the data may be rejected, and the entire
color measuring process repeated. Again, unequal values of peaks P1
and P2 may be indicative, for example, that the probe was moved in
a non-perpendicular or otherwise unstable manner (i.e., angular or
lateral movement), and, for example, peak P1 may be representative
of a first point on the object, while peak P2 may be representative
of a second point on the object. As the data is suspect, in a
preferred embodiment of the present invention, data taken in such
circumstances are rejected in step 64.
[0121] If the data are not rejected in step 64, the process
proceeds to step 66. In step 66, the system analyzes the data taken
from the neutral-density-filtered receivers from each of the
perimeter fiber optics (e.g., R1 to R3 of FIG. 2). If the peaks of
the perimeter fiber optics did not occur at or about the same point
in time, this may be indicative, for example, that the probe was
not held perpendicular to the surface of the object being measured.
As non-perpendicular alignment of the probe with the surface of the
object being measured may cause suspect results, in a preferred
embodiment of the present invention, data taken in such
circumstances are rejected in step 66. In one preferred embodiment,
detection of simultaneous or near simultaneous peaking (peaking
within a predetermined range of time) serves as an acceptance
criterion for the data, as perpendicular alignment generally is
indicated by simultaneous or near simultaneous peaking of the
perimeter fiber optics. In other embodiments, step 66 includes an
analysis of peak values P1 and P2 of the perimeter fiber optics. In
such embodiments, the system seeks to determine if the peak values
of the perimeter fiber optics (perhaps normalized with any initial
calibration data) are equal within a defined range. If the peak
values of the perimeter fiber optics are within the defined range,
the data may be accepted, and if not, the data may be rejected. In
still other embodiments, a combination of simultaneous peaking and
equal value detection are used as acceptance/rejection criteria for
the data, and/or the operator may have the ability (such as through
key pad switches 12) to control one or more of the acceptance
criteria ranges. With such capability, the sensitivity of the
system may be controllably altered by the operator depending upon
the particular application and operative environment, etc.
[0122] If the data are not rejected in step 66, the process
proceeds to step 68. In step 68, the color data may be processed in
a desired manner to produce output color/optical measurement data.
For example, such data may be normalized in some manner, or
adjusted based on temperature compensation, or translucency data,
or gloss data or surface texture data or non-perpendicular angle
data other data detected by the system. The data also may be
converted to different display or other formats, depending on the
intended use of the data. In addition, the data indicative of the
translucence of the object and/or glossiness of the object also may
be quantified and/or displayed in step 68. After step 68, the
process may proceed to starting step 49, or the process may be
terminated, etc. As indicated previously, such data also may be
compared with previously-stored data for purposes of making
assessments or predictions, etc., of a current or future condition
or status.
[0123] In accordance with the process illustrated in FIG. 6, three
light intensity values (P1, P2 and IS) are stored per receiver
fiber optic to make color and translucency, etc., measurements. If
stored peak values P1 and P2 are not equal (for some or all of the
receivers), this is an indication that the probe was not held
steady over one area, and the data may be rejected (in other
embodiments, the data may not be rejected, although the resulting
data may be used to produce an average of the measured data). In
addition, peak values P1 and P2 for the three neutral density
perimeter fiber optics should be equal or approximately equal; if
this is not the case, then this is an indication that the probe was
not held perpendicular or a curved surface is being measured. In
other embodiments, the system attempts to compensate for curved
surfaces and/or non-perpendicular angles. In any event, if the
system cannot make a color/optical measurement, or if the data is
rejected because peak values P1 and P2 are unequal to an
unacceptable degree or for some other reason, then the operator is
notified so that another measurement or other action may be taken
(such as adjust the sensitivity).
[0124] With a system constructed and operating as described above,
color/optical measurements may be taken of an object, with accepted
data having height and angular dependencies removed. Data not taken
at the peaking height, or data not taken with the probe
perpendicular to the surface of the object being measured, etc.,
are rejected in certain embodiments. In other embodiments, data
received from the perimeter fiber optics may be used to calculate
the angle of the probe with respect to the surface of the object
being measured, and in such embodiments non-perpendicular or curved
surface data may be compensated instead of rejected. It also should
be noted that peak values P1 and P2 for the neutral density
perimeter fiber optics provide a measurement of the luminance (gray
value) of the surface of the object being measured, and also may
serve to quantify the color value.
[0125] The translucency of the object being measured may be
quantified as a ratio or percentage, such as, for example,
(IS/P1).times.100%. In other embodiments, other methods of
quantifying translucency data provided in accordance with the
present invention are utilized, such as some other arithmetic
function utilizing IS and P1 or P2, etc. Translucence information,
as would be known to those in the art, could be used to quantify
and/or adjust the output color data, etc.
[0126] In another particular aspect of the present invention, data
generated in accordance with the present invention may be used to
implement an automated material mixing/generation machine and/or
method. Certain objects/materials, such as dental prostheses or
fillings, are made from porcelain or other powders/resins/materials
or tissue substitutes that may be combined in the correct ratios or
modified with additives to form the desired color of the
object/prosthesis. Certain powders often contain pigments that
generally obey Beer's law and/or act in accordance with
Kubelka-Munk equations and/or Saunderson equations (if needed) when
mixed in a recipe. Color and other data taken from a measurement in
accordance with the present invention may be used to determine or
predict desired quantities of pigment or other materials for the
recipe. Porcelain powders and other materials are available in
different colors, opacities, etc. Certain objects, such as dental
prostheses, may be layered to simulate the degree of translucency
of the desired object (such as to simulate a human tooth). Data
generated in accordance with the present invention also may be used
to determine the thickness and position of the porcelain or other
material layers to more closely produce the desired color,
translucency, surface characteristics, etc. In addition, based on
fluorescence data for the desired object, the material recipe may
be adjusted to include a desired quantity of fluorescing-type
material. In yet other embodiments, surface characteristics (such
as texture) information (as more fully described herein) may be
used to add a texturing material to the recipe, all of which may be
carried out in accordance with the present invention. In yet other
embodiments, the degree of surface polish to the prosthesis may be
monitored or adjusted, based on gloss data derived in accordance
with the present invention.
[0127] For more information regarding such pigment-material recipe
type technology, reference may be made to: "The Measurement of
Appearance," Second Edition, edited by Hunter and Harold, copyright
1987; "Principles of Color Technology," by Billmeyer and Saltzman,
copyright 1981; and "Pigment Handbook," edited by Lewis, copyright
1988. All of the foregoing are believed to have been published by
John Wiley & Sons, Inc., New York, N.Y., and all of which are
hereby incorporated by reference.
[0128] In certain operative environments, such as dental
applications, contamination of the probe is of concern. In certain
embodiments of the present invention, implements to reduce such
contamination are provided.
[0129] FIGS. 7A and 7B illustrate a protective cap that may be used
to fit over the end of probe tip 1. Such a protective cap consists
of body 80, the end of which is covered by optical window 82, which
in a preferred embodiment consists of a structure having a thin
sapphire window. In a preferred embodiment, body 80 consists of
stainless steel. Body 80 fits over the end of probe tip 1 and may
be held into place by, for example, indentations formed in body 80,
which fit with ribs 84 (which may be a spring clip or other
retainer) formed on probe tip 1. In other embodiments, other
methods of affixing such a protective cap to probe tip 1 are
utilized. The protective cap may be removed from probe tip 1 and
sterilized in a typical autoclave, hot steam, chemiclave or other
sterilizing system.
[0130] The thickness of the sapphire window should be less than the
peaking height of the probe in order to preserve the ability to
detect peaking in accordance with the present
invention, and preferably has a thickness less than the critical
height at which the source/receiver cones overlap (see FIGS. 4B and
4C). It also is believed that sapphire windows may be manufactured
in a reproducible manner, and thus any light attenuation from one
cap to another may be reproducible. In addition, any distortion of
the color/optical measurements produced by the sapphire window may
be calibrated out by microprocessor 10.
[0131] Similarly, in other embodiments body 80 has a cap with a
hole in the center (as opposed to a sapphire window), with the hole
positioned over the fiber optic source/receivers
The cap with the hole serves to prevent the probe from coming into
contact with the surface, thereby reducing the risk of
contamination. It should be noted that, with such embodiments, the
hole is positioned so that the light from/to the light
source/receiver elements of the probe tip is not adversely affected
by the cap.
[0132] FIGS. 8A and 8B illustrate another embodiment of a removable
probe tip that may be used to reduce contamination in accordance
with the present invention. As illustrated in FIG. 8A, probe tip 88
is removable, and includes four (or a different number, depending
upon the application) fiber optic connectors 90, which are
positioned within optical guard 92 coupled to connector 94. Optical
guard 92 serves to prevent "cross talk" between adjacent fiber
optics. As illustrated in FIG. 8B, in this embodiment removable tip
88 is secured in probe tip housing 93 by way of spring clip 96
(other removable retaining implements are utilized in other
embodiments). Probe tip housing 93 may be secured to base connector
95 by a screw or other conventional fitting. It should be noted
that, with this embodiment, different size tips may be provided for
different applications, and that an initial step of the process may
be to install the properly-sized (or fitted tip) for the particular
application. Removable tip 88 also may be sterilized in a typical
autoclave, hot steam, chemiclave or other sterilizing system, or
disposed of. In addition, the entire probe tip assembly is
constructed so that it may be readily disassembled for cleaning or
repair. In certain embodiments the light source/receiver elements
of the removable tip are constructed of glass, silica or similar
materials, thereby making them particularly suitable for autoclave
or similar high temperature/pressure cleaning methods, which in
certain other embodiments the light source/receiver elements of the
removable tip are constructed of plastic or other similar
materials, which may be of lower cost, thereby making them
particularly suitable for disposable-type removable tips, etc.
[0133] In still other embodiments, a plastic, paper or other type
shield (which may be disposable, cleanable/reusable or the like)
may be used in order to address any contamination concerns that may
exist in the particular application. In such embodiments, the
methodology may include positioning such a shield over the probe
tip prior to taking color/optical measurements, and may include
removing and disposing/cleaning the shield after taking
color/optical measurements, etc.
[0134] A further embodiment of the present invention utilizing an
alternate removable probe tip will now be described with reference
to FIGS. 23A-23C. As illustrated in FIG. 23A, this embodiment
utilizes removable, coherent light conduit 340 as a removable tip.
Light conduit 340 is a short segment of a light conduit that
preferably may be a fused bundle of small fiber optics, in which
the fibers are held essentially parallel to each other, and the
ends of which are highly polished. Cross-section 350 of light
conduit 340 is illustrated in FIG. 23B. Light conduits similar to
light conduit 340 have been utilized in what are known as
borescopes, and also have been utilized in medical applications
such as endoscopes.
[0135] Light conduit 340 in this embodiment serves to conduct light
from the light source to the surface of the object being measured,
and also to receive reflected light from the surface and conduct it
to light receiver fiber optics 346 in probe handle 344. Light
conduit 340 is held in position with respect to fiber optics 346 by
way or compression jaws 342 or other suitable fitting or coupled
that reliably positions light conduit 340 so as to couple light
effectively to/from fiber optics 346. Fiber optics 346 may be
separated into separate fibers/light conduits 348, which may be
coupled to appropriate light sensors, etc., as with previously
described embodiments.
[0136] In general, the aperture of the fiber optics used in light
conduit 340 may be chosen to match the aperture of the fiber optics
for the light source and the light receivers or alternately the
light conduit aperture could be greater than or equal to the
largest source or receiver aperture. Thus, the central part of the
light conduit may conduct light from the light source and
illuminate the surface as if it constituted a single fiber within a
bundle of fibers. Similarly, the outer portion of the light conduit
may receive reflected light and conduct it to light receiver fiber
optics as if it constituted single fibers. Light conduit 340 has
ends that preferably are highly polished and cut perpendicular,
particularly the end coupling light to fiber optics 346. Similarly,
the end of fiber optics 346 abutting light conduit 340 also is
highly polished and cut perpendicular to a high degree of accuracy
in order to minimize light reflection and cross talk between the
light source fiber optic and the light receiver fiber optics and
between adjacent receiver fiber optics. Light conduit 340 offers
significant advantages including in the manufacture and
installation of such a removable tip. For example, the probe tip
need not be particularly aligned with the probe tip holder; rather,
it only needs to be held against the probe tip holder such as with
a compression mechanism (such as with compression jaws 342) so as
to couple light effectively to/from fiber optics 346. Thus, such a
removable tip mechanism may be implemented without alignment tabs
or the like, thereby facilitating easy installation of the
removable probe tip. Such an easy installable probe tip may thus be
removed and cleaned prior to installation, thereby facilitating use
of the color/optical measuring apparatus by dentists, medical
professions or others working in an environment in which
contamination may be a concern. Light conduit 340 also may be
implemented, for example, as a small section of light conduit,
which may facilitate easy and low cost mass production and the
like.
[0137] A further embodiment of such a light conduit probe tip is
illustrated as light conduit 352 in FIG. 23C. Light conduit 352 is
a light conduit that is narrower on one end (end 354) than the
other end (end 356). Contoured/tapered light conduits such as light
conduit 352 may be fabricated by heating and stretching a bundle of
small fiber optics as part of the fusing process. Such light
conduits have an additional interesting property of magnification
or reduction. Such phenomena result because there are the same
number of fibers in both ends. Thus, light entering narrow end 354
is conducted to wider end 356, and since wider end 356 covers a
larger area, it has a magnifying affect.
[0138] Light conduit 352 of FIG. 23C may be utilized in a manner
similar to light conduit 340 (which in general may be cylindrical)
of FIG. 23A. Light conduit 352, however, measures smaller areas
because of its reduced size at end 354. Thus, a relatively larger
probe body may be manufactured where the source fiber optic is
spaced widely from the receiver fiber optics, which may provide an
advantage in reduced light reflection and cross talk at the
junction, while still maintaining a small probe measuring area.
Additionally, the relative sizes of narrow end 354 of light conduit
352 may be varied. This enables the operator to select the
size/characteristic of the removable probe tip according to the
conditions in the particular application. Such ability to select
sizes of probe tips provides a further advantage in making optical
characteristics measurements in a variety of applications and
operative environments.
[0139] As should be apparent to those skilled in the art in view of
the disclosures herein, light conduits 340 and 356 of FIGS. 23A and
23C need not necessarily be cylindrical/tapered as illustrated, but
may be curved such as for specialty applications, in which a curved
probe tip may be advantageously employed (such as in a confined or
hard-to-reach place). It also should be apparent that light conduit
352 of FIG. 23C may be reversed (with narrow end 354 coupling light
into fiber optics 346, etc., and wide end 356 positioned in order
to take measurements) in order to cover larger areas.
[0140] With reference to FIG. 9, a tristimulus embodiment will now
be described, which may aid in the understanding of, or may be used
in conjunction with, certain embodiments disclosed herein. In
general, the overall system depicted in FIG. 1 and discussed in
detail elsewhere herein may be used with this embodiment. FIG. 9
illustrates a cross section of the probe tip fiber optics used in
this embodiment.
[0141] Probe tip 100 includes central source fiber optic 106,
surrounded by (and spaced apart from) three perimeter receiver
fiber optics 104 and three color receiver fiber optics 102. Three
perimeter receiver fiber optics 104 are optically coupled to
neutral density filters and serve as height/angle sensors in a
manner analogous to the embodiment describe above. Three color
receiver fiber optics are optically coupled to suitable tristimulus
filters, such as red, green and blue filters. With this embodiment,
a measurement may be made of tristimulus color values of the
object, and the process described with reference to FIG. 6
generally is applicable to this embodiment. In particular,
perimeter fiber optics 104 may be used to detect simultaneous
peaking or otherwise whether the probe is perpendicular to the
object being measured.
[0142] FIG. 10A illustrates another such embodiment, similar to the
embodiment discussed with reference to FIG. 9. Probe tip 100
includes central source fiber optic 106, surrounded by (and spaced
apart from) three perimeter receiver fiber optics 104 and a
plurality of color receiver fiber optics 102. The number of color
receiver fiber optics 102, and the filters associated with such
receiver fiber optics 102, may be chosen based upon the particular
application. As with the embodiment of FIG. 9, the process
described with reference to FIG. 6 generally is applicable to this
embodiment.
[0143] FIG. 10B illustrates another such embodiment in which there
are a plurality of receiver fiber optics that surround central
source fiber optic 240. The receiver fiber optics are arranged in
rings surrounding the central source fiber optic. FIG. 10B
illustrates three rings of receiver fiber optics (consisting of
fiber optics 242, 244 and 246, respectively), in which there are
six receiver fiber optics per ring. The rings may be arranged in
successive larger circles as illustrated to cover the entire area
of the end of the probe, with the distance from each receiver fiber
optic within a given ring to the central fiber optic being equal
(or approximately so). Central fiber optic 240 is utilized as the
light source fiber optic and is connected to the light source in a
manner similar to light source fiber optic 5 illustrated in FIG.
1.
[0144] The plurality of receiver fiber optics are each coupled to
two or more fiber optics in a manner similar to the arrangement
illustrated in FIG. 1 for splicing connector 4. One fiber optic
from such a splicing connector for each receiver fiber optic passes
through a neutral density filter and then to light sensor circuitry
similar to the light sensor circuitry illustrated in FIG. 3. A
second fiber optic from the splicing connector per receiver fiber
optic passes through a Sharp Cutting Wrattan Gelatin Filter (or
notch filter as previously described) and then to light sensor
circuitry as discussed elsewhere herein. Thus, each of the receiver
fiber optics in the probe tip includes both color measuring
elements and neutral light measuring or "perimeter" elements.
[0145] FIG. 10D illustrates the geometry of probe 260 (such as
described above) illuminating an area on flat diffuse surface 272.
Probe 260 creates light pattern 262 that is reflected diffusely
from surface 272 in uniform hemispherical pattern 270. With such a
reflection pattern, the reflected light that is incident upon the
receiving elements in the probe will be equal (or nearly equal) for
all elements if the probe is perpendicular to the surface as
described above herein.
[0146] FIG. 10C illustrates a probe illuminating rough surface 268
or a surface that reflects light unevenly. The reflected light will
exhibit hot spots or regions 266 where the reflected light
intensity is considerably greater than it is on other areas 264.
The reflected light pattern will be uneven when compared to a
smooth surface as illustrate in FIG. 10D.
[0147] Since a probe as illustrated in FIG. 10B has a plurality of
receiver fiber optics arranged over a large surface area, the probe
may be utilized to determine the surface texture of the surface as
well as being able to measure the color and translucency, etc., of
the surface as described earlier herein. If the light intensity
received by the receiver fiber optics is equal for all fiber optics
within a given ring of receiver fiber optics, then generally the
surface is smooth. If, however, the light intensity of receiver
fibers in a ring varies with respect to each other, then generally
the surface is rough. By comparing the light intensities measured
within receiver fiber optics in a given ring and from ring to ring,
the texture and other characteristics of the surface may be
quantified.
[0148] FIG. 11 illustrates an embodiment of the present invention
in which linear optical sensors and a color gradient filter are
utilized instead of light sensors 8 (and filters 22, etc.).
Receiver fiber optics 7, which may be optically coupled to probe
tip 1 as with the embodiment of FIG. 1, are optically coupled to
linear optical sensor 112 through color gradient filter 110. In
this embodiment, color gradient filter 110 may consist of series of
narrow strips of cut-off type filters on a transparent or open
substrate, which are constructed so as to positionally correspond
to the sensor areas of linear optical sensor 112. An example of a
commercially available linear optical sensor 112 is Texas
Instruments part number TSL213, which has 61 photo diodes in a
linear array. Light receiver fiber optics 7 are arranged
correspondingly in a line over linear optical sensor 112. The
number of receiver fiber optics may be chosen for the particular
application, so long as enough are included to more or less evenly
cover the full length of color gradient filter 110. With this
embodiment, the light is received and output from receiver fiber
optics 7, and the light received by linear optical sensor 112 is
integrated for a short period of time (determined by the light
intensity, filter characteristics and desired accuracy). The output
of linear array sensor 112 is digitized by ADC 114 and output to
microprocessor 116 (which may the same processor as microprocessor
10 or another processor).
[0149] In general, with the embodiment of FIG. 11, perimeter
receiver fiber optics may be used as with the embodiment of FIG. 1,
and in general the process described with reference to FIG. 6 is
applicable to this embodiment.
[0150] FIG. 12 illustrates an embodiment of the present invention
in which a matrix optical sensor and a color filter grid are
utilized instead of light sensors 8 (and filters 22, etc.).
Receiver fiber optics 7, which may be optically coupled to probe
tip 1 as with the embodiment of FIG. 1, are optically coupled to
matrix optical sensor 122 through filter grid 120. Filter grid 120
is a filter array consisting of a number of small colored spot
filters that pass narrow bands of visible light. Light from
receiver fiber optics 7 pass through corresponding filter spots to
corresponding points on matrix optical sensor 122. In this
embodiment, matrix optical sensor 122 may be a monochrome optical
sensor array, such as CCD-type or other type of light sensor
element such as may be used in a video camera. The output of matrix
optical sensor 122 is digitized by ADC 124 and output to
microprocessor 126 (which may the same processor as microprocessor
10 or another processor). Under control of microprocessor 126,
matrix optical sensor 126 collects data from receiver fiber optics
7 through color filter grid 120.
[0151] In general, with the embodiment of FIG. 12, perimeter
receiver fiber optics may be used as with the embodiment of FIG. 1,
and in general the process described with reference to FIG. 6 also
is applicable to this embodiment.
[0152] In general with the embodiments of FIGS. 11 and 12, the
color filter grid may consist of sharp cut off filters as described
earlier or it may consist of notch filters. As will be apparent to
one skilled in the art, they may also be constructed of a
diffraction grating and focusing mirrors such as those utilized in
conventional monochromators.
[0153] As will be clear from the foregoing description, with the
present invention a variety of types of spectral color/optical
photometers (or tristimulus-type colorimeters) may be constructed,
with perimeter receiver fiber optics used to collect color/optical
data essentially free from height and angular deviations. In
addition, in certain embodiments, the present invention enables
color/optical measurements to be taken at a peaking height from the
surface of the object being measured, and thus color/optical data
may be taken without physical contact with the object being
measured (in such embodiments, the color/optical data is taken only
by passing the probe through region 1 and into region 2, but
without necessarily going into region 3 of FIGS. 5A and 5B). Such
embodiments may be utilized if contact with the surface is
undesirable in a particular application. In the embodiments
described earlier, however, physical contact (or near physical
contact) of the probe with the object may allow all five regions of
FIGS. 5A and 5B to be utilized, thereby enabling measurements to be
taken such that translucency information also may be obtained. Both
types of embodiments generally are within the scope of the
invention described herein.
[0154] Additional description will now be provided with respect to
cut-off filters of the type described in connection with the
preferred embodiment(s) of FIGS. 1 and 3 (such as filters 22 of
FIG. 3). FIG. 13A illustrates the properties of a single Kodak
Sharp Cutting Wratten Gelatin Filter discussed in connection with
FIG. 3. Such a cut-off filter passes light below a cut-off
frequency (i.e., above a cut-off wavelength). Such filters may be
manufactured to have a wide range of cut-off
frequencies/wavelengths. FIG. 13B illustrates a number of such
filters, twelve in a preferred embodiment, with cut-off
frequencies/wavelengths chosen so that essentially the entire
visible band is covered by the collection of cut-off filters.
[0155] FIGS. 14A and 14B illustrate exemplary intensity
measurements using a cut-off filter arrangement such as illustrated
in FIG. 13B, first in the case of a white surface being measured
(FIG. 14A), and also in the case of a blue surface being measured
(FIG. 14B). As illustrated in FIG. 14A, in the case of a white
surface, the neutrally filtered perimeter fiber optics, which are
used to detect height and angle, etc., generally will produce the
highest intensity (although this depends at least in part upon the
characteristics of the neutral density filters). As a result of the
stepped cut-off filtering provided by filters having the
characteristics illustrated in FIG. 13B, the remaining intensities
will gradually decrease in value as illustrated in FIG. 14A. In the
case of a blue surface, the intensities will decrease in value
generally as illustrated in FIG. 14B. Regardless of the surface,
however, the intensities out of the filters will always decrease in
value as illustrated, with the greatest intensity value being the
output of the filter having the lowest wavelength cut-off value
(i.e., passes all visible light up to blue), and the lowest
intensity value being the output of the filter having the highest
wavelength cut-off (i.e., passes only red visible light). As will
be understood from the foregoing description, any color data
detected that does not fit the decreasing intensity profiles of
FIGS. 14A and 14B may be detected as an abnormality, and in certain
embodiments detection of such a condition results in data
rejection, generation of an error message or initiation of a
diagnostic routine, etc.
[0156] Reference should be made to the FIGS. 1 and 3 and the
related description for a detailed discussion of how such a cut-off
filter arrangement may be utilized in accordance with the present
invention.
[0157] FIG. 15 is a flow chart illustrating audio tones that may be
used in certain preferred embodiments of the present invention. It
has been discovered that audio tones (such as tones, beeps, voice
or the like such as will be described) present a particularly
useful and instructive means to guide an operator in the proper use
of a color measuring system of the type described herein.
[0158] The operator may initiate a color/optical measurement by
activation of a switch (such as switch 17 of FIG. 1) at step 150.
Thereafter, if the system is ready (set-up, initialized,
calibrated, etc.), a lower-the-probe tone is emitted (such as
through speaker 16 of FIG. 1) at step 152. The system attempts to
detect peak intensity P1 at step 154. If a peak is detected, at
step 156 a determination is made whether the measured peak P1 meets
the applicable criteria (such as discussed above in connection with
FIGS. 5A, 5B and 6). If the measured peak P1 is accepted, a first
peak acceptance tone is generated at step 160. If the measured peak
P1 is not accepted, an unsuccessful tone is generated at step 158,
and the system may await the operator to initiate a further
color/optical measurement. Assuming that the first peak was
accepted, the system attempts to detect peak intensity P2 at step
162. If a second peak is detected, at step 164 a determination is
made whether the measured peak P2 meets the applicable criteria. If
the measured peak P2 is accepted the process proceeds to color
calculation step 166 (in other embodiments, a second peak
acceptance tone also is generated at step 166). If the measured
peak P2 is not accepted, an unsuccessful tone is generated at step
158, and the system may await the operator to initiate a further
color/optical measurement. Assuming that the second peak was
accepted, a color/optical calculation is made at step 166 (such as,
for example, microprocessor 10 of FIG. 1 processing the data output
from light sensors 8, etc.). At step 168, a determination is made
whether the color calculation meets the applicable criteria. If the
color calculation is accepted, a successful tone is generated at
step 170. If the color calculation is not accepted, an unsuccessful
tone is generated at step 158, and the system may await the
operator to initiate a further color/optical measurement.
[0159] With unique audio tones presented to an operator in
accordance with the particular operating state of the system, the
operator's use of the system may be greatly facilitated. Such audio
information also tends to increase operator satisfaction and skill
level, as, for example, acceptance tones provide positive and
encouraging feedback when the system is operated in a desired
manner.
[0160] The color/optical measuring systems and methods in
accordance with the present invention may be applied to particular
advantage in the field of dentistry, as will be more fully
explained hereinafter. In particular the present invention includes
the use of such systems and methods to measure the color and other
attributes of a tooth in order to prepare a dental prosthesis or
intraoral tooth-colored fillings, or to select denture teeth or to
determine a suitable cement color for porcelain/resin prostheses.
The present invention also provides methods for storing and
organizing measured data such as in the form of a patient
database.
[0161] FIG. 16A is a flow chart illustrating a general dental
application process flow for use of the color/optical measuring
systems and methods in accordance with the present invention. At
step 200, the color/optical measuring system may be powered-up and
stabilized, with any required initialization or other setup
routines performed. At step 200, an indication of the system status
may be provided to the operator, such as through LCD 14 or speaker
16 of FIG. 1. Also at step 200, the probe tip may be shielded or a
clean probe tip may be inserted in order to reduce the likelihood
of contamination (see, e.g., FIGS. 7A to 8B and related
description). In other embodiments, a plastic or other shield may
also be used (which may be disposable, cleanable/reusable, etc., as
previously described), so long as it is constructed and/or
positioned so as to not adversely affect the measurement
process.
[0162] At step 202, the patient and the tooth to be measured are
prepared. Any required cleaning or other tooth preparation would be
performed at step 202. Any required patient consultation about the
type of prosthesis or area of a tooth to be matched would be
performed at (or before) step 202. In certain embodiments, a
positioning device is prepared at step 202, such as is illustrated
in FIGS. 17A and 17B. In such embodiments, for example, a black or
other suitably-colored material 282, which may adhere to tooth 280
(such as with a suitable adhesive), is formed to have opening 281
larger than the diameter of the measuring probe, with opening 281
centered on the area of tooth 280 to be measured. The material of
positioning device 282 is formed in a manner to fit on/over tooth
280 (such as over the incisal edge of tooth 280 and/or over one or
more adjacent teeth) so that it may be placed on/over tooth 280 in
a repeatable manner. Such a positioning device may serve to ensure
that the desired area of tooth 280 is measured, and also allows for
repeat measurements of the same area for purposes of confirmation,
fluorescence measurement, or other optical measurement, or the
like. Any other pre-measurement activities may be performed at (or
before) step 202.
[0163] At step 204, the operator (typically a dentist or other
dental professional) moves the probe towards the area of the tooth
to be measured. This process preferably is conducted in accordance
with the methodology described with reference to FIGS. 5A, 5B and
6, and preferably is accompanied by audio tones such as described
with reference to FIG. 15. With the present invention, the operator
may obtain color and translucency data, etc., for example, from a
desired area of the tooth to be measured. During step 204, an
accepted color/optical measurement is made, or some indication is
given to the operator that the measurement step needs to be
repeated or some other action taken. After an accepted
color/optical measurement is made at step 204, for example, the
dentist may operate on the desired tooth or teeth or take other
action. Before or after such action, additional measurements may be
taken as needed (see, e.g., FIG. 18 and related description).
[0164] Upon successful completion of one or more measurements taken
at step 204, the process proceeds to step 206. At step 206, any
data conversion or processing of data collected at step 204 may be
performed. For example, in the embodiment of FIG. 1, detailed color
spectrum and translucency information may be generated. In a
particular dental application, however, it may be that a dental
lab, for example, requires that the color be presented in Munsell
format (i.e., chroma, hue and value), RGB values, XYZ coordinates,
CIELAB values, Hunter values, or some other color data format. With
the spectral/color information produced by the present invention,
data may be converted to such formats through conventional math,
for example. Such math may be performed by microprocessor 10 or
computer 13A of FIG. 1, or in some other manner. It also should be
noted that, in certain embodiments, the data produced at step 204
in accordance with the present invention may be used directly
without data conversion. In such embodiments, step 206 may be
omitted. In other embodiments, step 206 consists of data
formatting, such as preparing the data for reproduction in hard
copy, pictorial or other form, or for transmission as facsimile or
modem data. Finally, in certain embodiments a translucency factor
is computed in a format suitable for the particular application. In
yet other embodiments, a surface texture or detail factor is
computed in a format suitable for the particular application. In
yet other embodiments, a surface gloss factor is computed in a
format suitable for the particular application.
[0165] At step 208, a matching is optionally attempted between the
data produced at steps 204 and 206 (if performed) and a desired
color (in other embodiments, the process may proceed from 204
directly to 210, or alternatively steps 206 and 208 may be
combined). For example, a number of "shade guides" are available in
the market, some of which are known in the industry as Vita shade
guides, Bioform shade guides or other color matching standards,
guides or references or custom shade guides. In certain preferred
embodiments, a lookup table is prepared and loaded into memory
(such as memory associated with microprocessor 10 or computer 13A
of FIG. 1), and an attempt is made to the closest match or matches
of the collected data with the known shade guides, custom shade
guides or reference values. In certain embodiments, a translucency
factor and/or gloss factor and/or a surface texture or detail
factor also is used in an effort to select the best possible
match.
[0166] In a particular aspect of certain embodiments of the present
invention, at step 208 a material correlation lookup table is
accessed. Based on the color and translucency data obtained at step
204, a proposed recipe of materials, pigments or other instruction
information is prepared for a prosthesis or filling, etc., of the
desired color and translucency, etc. With the detailed color and
other information made available in accordance with the present
invention, a direct correlation with the relevant constituent
materials may be made. In still other embodiments, such information
is made available to an automated mixing or manufacturing machine
for preparation of prosthesis or material of the desired color and
translucency, etc., as more fully described elsewhere herein.
[0167] At step 210, based on the results of the preceding steps,
the prosthesis, denture, intraoral tooth-colored filling material
or other items are prepared. This step may be performed at a dental
lab, or, in certain embodiments, at or near the dental operatory.
For remote preparation, relevant data produced at steps 204, 206
and/or 208 may be sent to the remote lab or facility by hardcopy,
facsimile or modem or other transmission. What should be understood
from the foregoing is that, based on data collected at step 204, a
prosthesis may be prepared of a desirable color and/or other
optical characteristic at step 210.
[0168] At step 212, the prosthesis or other material prepared at
step 210 may be measured for confirmation purposes, again
preferably conducted in accordance with the methodology described
with reference to FIGS. 5A, 5B and 6, and preferably accompanied by
audio tones such as described with reference to FIG. 15. A
re-measure of the tooth in the patient's mouth, etc. also may be
made at this step for confirmation purposes. If the confirmation
process gives satisfactory results, the prosthesis, denture,
composite filling or other material may be preliminarily installed
or applied in the patient at step 214. At step 216, a re-measure of
the prosthesis, denture, composite filling or other materials
optionally may be made. If the results of step 216 are acceptable,
then the prosthesis may be more permanently installed or applied in
the patient at step 218. If the results of step 216 are not
acceptable, the prosthesis may be modified and/or other of the
steps repeated as necessary in the particular situation.
[0169] With reference to FIG. 16B, a further embodiment of the
present invention will be explained. With this embodiment, an
instrument and method such as previously described may be
advantageously utilized to prepare a tooth to receive a
prosthesis.
[0170] A dental prosthesis such as a crown or a laminate has
optical properties that are determined by a number of factors.
Determining factors include the material of the prosthesis, along
with the cement utilized to bond the prosthesis to the tooth and
the underlying optical properties of the tooth itself. For example,
in the preparation of a tooth for a laminate, the thickness of the
laminate combined with the bonding cement and the color of the
underlying prepared tooth all contribute to the final optical
properties of the prosthesis. In order to prepare an optimum
prosthesis such as from an esthetic standpoint, the dentist may
need to prepare the tooth for the laminate by removing material
from the tooth. The final desired esthetic color, shape and
contours of the tooth determines the amount of material needed to
be removed from the tooth, which determines the final thickness of
the laminate, and in significant part may determine whether or not
the final restoration will have a desired and esthetically pleasing
result as compared to neighboring teeth. By measuring the color of
the neighboring teeth, and by measuring the color of the underlying
tooth being prepared for the laminate, the amount of tooth material
to be removed, or the range of material that should be removed, may
be determined and reported to the dentist as the tooth is being
prepared.
[0171] At step 201, the process is commenced. Any initial
calibration or other preparatory steps may be undertaken. At step
203, the dentist may measure the optical properties including color
of one or more neighboring teeth. At step 205, the dentist may
measure the optical properties including color of the tooth
receiving the prosthesis. At step 207, a first amount of material
to be removed is calculated or estimated (such as by microprocessor
10, computer 13A or other suitable computing device). The first
amount is determined based on known color properties of the
available laminates, the estimated thickness of the laminate, and
the color of the tooth to receive the laminate. If, for example,
the tooth to receive the laminate is dark to the degree that an
esthetically pleasing laminate likely cannot be produced (based on
the range of color/optical characteristics of the known available
laminates), then an estimate is made of how much material should be
removed such that a thicker laminate will result in a desired and
esthetically pleasing result. At step 209 the dentist removes the
first amount of material (or approximately such amount) from the
tooth (using known removal techniques, etc.). At step 211, the
dentist may again measure the optical properties including color of
the tooth receiving the prosthesis. At step 213, a calculation or
estimation is made (in a manner analogous to step 207) of whether
additional material should be removed, and, if so, how much. At
step 215, if needed, additional material is removed, with steps
211, 213 and 215 repeated as necessary. In preferred embodiments,
based on known/measured/empirical data analysis of color/optical
properties of teeth, at steps such as steps 205 and 211, a
comparison or assessment may be made of whether the tooth being
prepared is getting too near the pulp (such as by detection of a
pink color, for example). Based on such threshold or other type
criteria, the dentist may be alerted that further material should
not be removed in order to minimize exposure of the pulp and damage
of the tooth. At step 217, if it is determined at step 213 that a
desirable and esthetically pleasing laminate may be produced, such
laminate preparation steps are conducted.
[0172] Similar steps could be taken in other industrial endeavors,
such as painting or other finishes, etc.
[0173] In another particular aspect of the present invention, for
example, data processing such as illustrated in FIG. 18 may be
taken in conjunction with the processes of FIGS. 16A and/or 16B. At
step 286, client database software is run on a computing device,
such as computer 13A of FIG. 1. Such software may include data
records for each patient, including fields storing the history of
dental services performed on the patient, information regarding the
status or condition of the patient's teeth, billing, address and
other information. Such software may enter a mode by which it is in
condition to accept color or other data taken in accordance with
the present invention.
[0174] At step 288, for example, the dentist or other dental
professional may select parameters for a particular tooth of the
patient to be measured. Depending on the size and condition of the
tooth (such as color gradient or the like), the dentist may sector
the tooth into one or more regions, such as a grid. Thus, for
example, in the case of tooth for which it is decided to take four
measurements, the tooth may be sectored into four regions. Such
parameters, which may include a pictorial representation on the
computer of the tooth sectored into four regions (such as by grid
lines), along with tooth identification and patient information may
be entered into the computer at this time.
[0175] At step 290, one or more measurements of the tooth may be
taken, such as with a system and method as described in connection
with FIGS. 1, 5A, 5B and/or 6. The number of such measurements
preferably is associated with the parameters entered at step 288.
Thereafter, at step 292, the data collected from the measurement(s)
may be sent to the computer for subsequent processing. As an
illustrative example, four color/optical measurements may be taken
(for the four regions of the tooth in the above example) and sent
to the computer, with the data for the four color/optical
measurements (such as RGB or other values) associated with the four
regions in accordance with the entered parameters. Also, as an
example, the displayed pictorial representation of the tooth may
have overlaid thereof data indicative of the color/optical
measurement(s). At step 294, such as after completion of
color/optical measurements on the particular patient, the data
collected during the process may be associatively stored as a part
of the patient's dental records in the data base. In embodiments
accompanied by use of an intraoral camera, for example (see, e.g.,
FIG. 19 and related description), captured images of one or more of
the patient's teeth also may be associatively stored as part of the
patient's dental records. In certain embodiments, a picture
captured by the intraoral camera is overlaid with grid or sector
lines (such as may be defined in step 288), with color or other
data measured as described herein also overlaid over the captured
image. In such a manner, the color or other data may be
electronically and visually associated with a picture of the
particular measured tooth, thereby facilitating the use of the
system and the understanding of the collected data. In still other
embodiments, all such captured image and color measurement records
include a time and/or date, so that a record of the particular
history of a particular tooth of a particular patient may be
maintained. See FIGS. 24 to 26 and 32 to 34 and related description
for additional embodiments utilizing an intraoral camera, etc., in
accordance with the present invention.
[0176] In yet another particular aspect of the present invention, a
measuring device and method (such as described elsewhere herein)
may be combined with an intraoral camera and other implements. As
illustrated in FIG. 19, control unit 300 contains conventional
electronics and circuitry, such as power supplies, control
electronics, light sources and the like. Coupled to control unit
300 is intraoral camera 301 (for viewing, and capturing images of,
a patient's tooth or mouth, etc.), curing light 302 (such as for
curing light-cured intraoral filling material), measuring device
304 (such as described elsewhere herein), and visible light 306
(which may be an auxiliary light for intraoral examinations and the
like). With such embodiments, color, translucency, fluorescence,
gloss, surface texture and/or other data collected for a particular
tooth from measuring device 304 may be combined with images
captured by intraoral camera 301, with the overall examination and
processing of the patient facilitated by having measuring device
304, intraoral camera 301, curing light 302 and visible light 306
integrated into a single unit. Such integration serves to provide
synergistic benefits in the use of the instruments, while also
reducing costs and saving physical space. In another particular
aspect of such embodiments, the light source for measuring device
304 and intraoral camera 301 are shared, thereby resulting in
additional benefits.
[0177] Further embodiments of the present invention will now be
described with reference to FIGS. 20 to 23. The previously
described embodiments generally rely on movement of the probe with
respect to the object/tooth being measured. While such embodiments
provide great utility in many applications, in certain
applications, such as robotics, industrial control, automated
manufacturing, etc. (such as positioning the object and/or the
probe to be in proximity to each other, detecting color/optical
properties of the object, and then directing the object, e.g.,
sorting, based on the detected color/optical properties, for
further industrial processing, packaging, etc.) it may be desired
to have the measurement made with the probe held or positioned
substantially stationary above the surface of the object to be
measured (in such embodiments, the positioned probe may not be
handheld as with certain other embodiments). Such embodiments also
may have applicability in the field of dentistry (in such
applications, "object" generally refers to a tooth, etc.).
[0178] FIG. 20 illustrates such a further embodiment. The probe of
this embodiment includes a plurality of perimeter sensors and a
plurality of color sensors coupled to receivers 312-320. The color
sensors and related components, etc., may be constructed to operate
in a manner analogous to previously described embodiments. For
example, fiber optic cables or the like may couple light from
source 310 that is received by receivers 312-320 to sharp cut-off
filters or to notch filters, with the received light measured over
precisely defined wavelengths (see, e.g., FIGS. 1, 3 and 11-14 and
related description). Color/optical characteristics of the object
may be determined from the plurality of color sensor measurements,
which may include three such sensors in the case of a tristimulus
instrument, or 8, 12, 15 or more color sensors for a more full
bandwidth system (the precise number may be determined by the
desired color resolution, etc.).
[0179] With this embodiment, a relatively greater number of
perimeter sensors are utilized (as opposed, for example, to the
three perimeter sensors used in certain preferred embodiments of
the present invention). As illustrated in FIG. 20, a plurality of
triads of receivers 312-320 coupled to perimeter sensors are
utilized, where each triad in the preferred implementation consists
of three fiber optics positioned equal distance from light source
310, which in the preferred embodiment is a central light source
fiber optic. The triads of perimeter receivers/sensors may be
configured as concentric rings of sensors around the central light
source fiber optic. In FIG. 20, ten such triad rings are
illustrated, although in other embodiments a lesser or greater
number of triad rings may be utilized, depending upon the desired
accuracy and range of operation, as well as cost considerations and
the like.
[0180] The probe illustrated in FIG. 20 may operate within a range
of heights (i.e., distances from the object being measured). As
with earlier embodiments, such height characteristics are
determined primarily by the geometry and constituent materials of
the probe, with the spacing of the minimal ring of perimeter
sensors determining the minimal height, and the spacing of the
maximal ring of perimeter sensors determining the maximum height,
etc. It therefore is possible to construct probes of various height
ranges and accuracy, etc., by varying the number of perimeter
sensor rings and the range of ring distances from the central
source fiber optic. It should be noted that such embodiments may be
particularly suitable when measuring similar types of materials,
etc.
[0181] As described earlier, the light receiver elements for the
plurality of receivers/perimeter sensors may be individual elements
such as Texas Instruments TSL230 light-to-frequency converters, or
may be constructed with rectangular array elements or the like such
as may be found in a CCD camera. Other broadband-type of light
measuring elements are utilized in other embodiments. Given the
large number of perimeter sensors used in such embodiments (such as
30 for the embodiment of FIG. 16), an array such as CCD camera-type
sensing elements may be desirable. It should be noted that the
absolute intensity levels of light measured by the perimeter
sensors is not as critical to such embodiments of the present
invention; in such embodiments differences between the triads of
perimeter light sensors are advantageously utilized in order to
obtain optical measurements.
[0182] Optical measurements may be made with such a probe by
holding/positioning the probe near the surface of the object being
measured (i.e., within the range of acceptable heights of the
particular probe). The light source providing light to light source
310 is turned on and the reflected light received by receivers
312-320 (coupled to the perimeter sensors) is measured. The light
intensity of the rings of triad sensors is compared. Generally, if
the probe is perpendicular to the surface and if the surface is
flat, the light intensity of the three sensors of each triad should
be approximately will be equal. If the probe is not perpendicular
to the surface or if the surface is not flat, the light intensity
of the three sensors within a triad will not be equal. It is thus
possible to determine if the probe is perpendicular to the surface
being measured, etc. It also is possible to compensate for
non-perpendicular surfaces by mathematically adjusting the light
intensity measurements of the color sensors with the variance in
measurements of the triads of perimeters sensors.
[0183] Since the three sensors forming triads of sensors are at
different distances (radii) from central light source 310, it is
expected that the light intensities measured by light receivers
312-320 and the perimeter sensors will vary. For any given triad of
sensors, as the probe is moved closer to the surface, the received
light intensity will increase to a maximum and then sharply
decrease as the probe is moved closer to the surface. As with
previously-described embodiments, the intensity decreases rapidly
as the probe is moved less than the peaking height and decreases
rapidly to zero or almost zero for opaque objects. The value of the
peaking height depends principally upon the distance of the
particular receiver from light source 310. Thus, the triads of
sensors will peak at different peaking heights. By analyzing the
variation in light values received by the triads of sensors, the
height of the probe can be determined. Again, this is particularly
true when measuring similar types of materials. As discussed
earlier, comparisons with previously-stored data also may be
utilized to made such determinations or assessments, etc.
[0184] The system initially is calibrated against a neutral
background (e.g., a gray background), and the calibration values
are stored in non-volatile memory (see, e.g., processor 10 of FIG.
1). For any given color or intensity, the intensity for the
receivers/perimeter sensors (independent of distance from the
central source fiber optic) in general should vary equally. Hence,
a white surface should produce the highest intensities for the
perimeter sensors, and a black surface will produce the lowest
intensities. Although the color of the surface will affect the
measured light intensities of the perimeter sensors, it should
affect them substantially equally. The height of the probe from the
surface of the object, however, will affect the triads of sensors
differently. At the minimal height range of the probe, the triad of
sensors in the smallest ring (those closest to the source fiber
optic) will be at or about their maximal value. The rest of the
rings of triads will be measuring light at intensities lower than
their maximal values. As the probe is raised/positioned from the
minimal height, the intensity of the smallest ring of sensors will
decrease and the intensity of the next ring of sensors will
increase to a maximal value and will then decrease in intensity as
the probe is raised/positioned still further. Similarly for the
third ring, fourth ring and so on. Thus, the pattern of intensities
measured by the rings of triads will be height dependent. In such
embodiments, characteristics of this pattern may be measured and
stored in non-volatile RAM look-up tables (or the like) for the
probe by calibrating it in a fixture using a neutral color surface.
Again, the actual intensity of light is not as important in such
embodiments, but the degree of variance from one ring of perimeter
sensors to another is.
[0185] To determine a measure of the height of the probe from the
surface being measured, the intensities of the perimeter sensors
(coupled to receivers 312-320) is measured. The variance in light
intensity from the inner ring of perimeter sensors to the next ring
and so on is analyzed and compared to the values in the look-up
table to determine the height of the probe. The determined height
of the probe with respect to the surface thus may be utilized by
the system processor to compensate for the light intensities
measured by the color sensors in order to obtain reflectivity
readings that are in general independent of height. As with
previously described embodiments, the reflectivity measurements may
then be used to determine optical characteristics of the object
being measured, etc.
[0186] It should be noted that audio tones, such as previously
described, may be advantageously employed when such an embodiment
is used in a handheld configuration. For example, audio tones of
varying pulses, frequencies and/or intensities may be employed to
indicate the operational status of the instrument, when the
instrument is positioned within an acceptable range for color
measurements, when valid or invalid color measurements have been
taken, etc. In general, audio tones as previously described may be
adapted for advantageous use with such further embodiments.
[0187] FIG. 21 illustrates a further such embodiment of the present
invention. The preferred implementation of this embodiment consists
of a central light source 310 (which in the preferred
implementation is a central light source fiber optic), surrounded
by a plurality of light receivers 322 (which in the preferred
implementation consists of three perimeter light receiver fiber
optics). The three perimeter light receiver fiber optics, as with
earlier described embodiments, may be each spliced into additional
fiber optics that pass to light intensity receivers/sensors, which
may be implemented with Texas Instruments TSL230 light to frequency
converters as described previously. One fiber of each perimeter
receiver is coupled to a sensor and measured full band width (or
over substantially the same bandwidth) such as via a neutral
density filter, and other of the fibers of the perimeter receivers
are coupled to sensors so that the light passes through sharp cut
off or notch filters to measure the light intensity over distinct
frequency ranges of light (again, as with earlier described
embodiments). Thus, there are color light sensors and neutral
"perimeter" sensors as with previously described embodiments. The
color sensors are utilized to determine the color or other optical
characteristics of the object, and the perimeter sensors are
utilized to determine if the probe is perpendicular to the surface
and/or are utilized to compensate for non-perpendicular angles
within certain angular ranges.
[0188] In the embodiment of FIG. 21, the angle of the perimeter
sensor fiber optics is mechanically varied with respect to the
central source fiber optic. The angle of the perimeter
receivers/sensors with respect to the central source fiber optic is
measured and utilized as described hereinafter. An exemplary
mechanical mechanism, the details of which are not critical so long
as desired, control movement of the perimeter receivers with
respect to the light source is obtained, is described with
reference to FIG. 22.
[0189] The probe is held within the useful range of the instrument
(determined by the particular configuration and construction,
etc.), and a color measurement is initiated. The angle of the
perimeter receivers/sensors with respect to the central light
source is varied from parallel to pointing towards the central
source fiber optic. While the angle is being varied, the
intensities of the light sensors for the perimeter sensors (e.g.,
neutral sensors) and the color sensors is measured and saved along
with the angle of the sensors at the time of the light measurement.
The light intensities are measured over a range of angles. As the
angle is increased the light intensity will increase to a maximum
value and will then decrease as the angle is further increased. The
angle where the light values is a maximum is utilized to determine
the height of the probe from the surface. As will be apparent to
those skilled in the art based on the teachings provided herein,
with suitable calibration data, simple geometry or other math,
etc., may be utilized to calculate the height based on the data
measured during variation of the angle. The height measurement may
then be utilized to compensate for the intensity of the
color/optical measurements and/or utilized to normalize color
values, etc.
[0190] FIG. 22 illustrates an exemplary embodiment of a mechanical
arrangement to adjust and measure the angle of the perimeter
sensors. Each perimeter receiver/sensor 322 is mounted with pivot
arm 326 on probe frame 328. Pivot arm 326 engages central ring 332
in a manner to form a cam mechanism. Central ring 332 includes a
groove that holds a portion of pivot arm 326 to form the cam
mechanism. Central ring 332 may be moved perpendicular with respect
to probe frame 328 via linear actuator 324 and threaded spindle
330. The position of central ring 332 with respect to linear
actuator 324 determines the angle of perimeter receivers/sensors
322 with respect to light source 310. Such angular position data
vis-a-vis the position of linear actuator 324 may be calibrated in
advance and stored in non-volatile memory, and later used to
produce color/optical characteristic measurement data as previously
described.
[0191] Referring now to FIG. 24, a further embodiment of the
present invention will be explained.
[0192] Intraoral reflectometer 380, which may be constructed as
described above, includes probe 381. Data output from reflectometer
380 is coupled to computer 384 over bus 390 (which may be a
standard serial or parallel bus, etc.). Computer 384 includes a
video freeze frame capability and preferably a modem. Intraoral
camera 382 includes handpiece 383 and couples video data to
computer 384 over bus 392. Computer 384 is coupled to remote
computer 386 over telecommunication channel 388, which may be a
standard telephone line, ISDN line, a LAN or WAN connection, etc.
With such an embodiment, video measurements may be taken of one or
more teeth by intraoral camera 382, along with optical measurements
taken by intraoral reflectometer 380. Computer 384 may store still
picture images taken from the output of intraoral camera 382.
[0193] Teeth are known to have variations in color from tooth to
tooth, and teeth are known to have variations in color over the
area of one tooth. Intraoral cameras are known to be useful for
showing the details of teeth. Intraoral cameras, however, in
general have poor color reproducibility. This is due to variations
in the camera sensing elements (from camera to camera and over time
etc.), in computer monitors, printers, etc. As a result of such
variations, it presently is not possible to accurately quantify the
color of a tooth with an intraoral camera. With the present
embodiment, measuring and quantifying the color or other optical
properties of teeth may be simplified through the use of an
intraoral reflectometer in accordance with the present invention,
along with an intraoral camera.
[0194] In accordance with this embodiment, the dentist may capture
a still picture of a tooth and its adjacent teeth using the freeze
frame feature of computer 384. Computer 384, under appropriate
software and operator control, may then "postureize" the image of
the tooth and its adjacent teeth, such as by limiting the number of
gray levels of the luminance signal, which can result in a color
image that shows contours of adjacent color boundaries. As
illustrated in FIG. 25, such a postureization process may result in
teeth 396 being divided into regions 398, which follow color
contours of teeth 396. As illustrated, in general the boundaries
will be irregular in shape and follow the various color variations
found on particular teeth.
[0195] With teeth postureized as illustrated in FIG. 25, computer
384 may then highlight (such as with a colored border, shading,
highlight or the like) a particular color region on a tooth to be
measured, and then the dentist may then measure the highlighted
region with intraoral reflectometer 380. The output of intraoral
reflectometer 380 is input to computer 384 over bus 390, and
computer 384 may store in memory or on a hard disk or other storage
medium the color/optical data associated with the highlighted
region. Computer 384 may then highlight another region and continue
the process until color/optical data associated with all desired
highlighted regions have been stored in computer 384. Such
color/optical data may then be stored in a suitable data base,
along with the video image and postureized video image of the
particular teeth, etc.
[0196] Computer 384 may then assess if the measured value of a
particular color region is consistent with color measurements for
adjacent color regions. If, for example, a color/optical
measurement for one region indicates a darker region as compared to
an adjacent region, but the postureized image indicates that the
reverse should be true, then computer 384 may notify the dentist
(such as with an audio tone) that one or more regions should be
re-measured with intraoral reflectometer 380. Computer 384 may make
such relative color determinations (even though the color values
stored in computer 384 from the freeze frame process are not true
color values) because the variations from region to region should
follow the same pattern as the color/optical measurements taken by
intraoral reflectometer 380. Thus, if one region is darker than its
neighbors, then computer 384 will expect that the color measurement
data from intraoral reflectometer 380 for the one region also will
be darker relative to color measurement data for the neighboring
regions, etc.
[0197] As with the optical characteristics measurement data and
captured images discussed previously, the postureized image of the
teeth, along with the color/optical measurement data for the
various regions of the teeth, may be conveniently stored,
maintained and accessed as part of the patient dental records. Such
stored data may be utilized advantageously in creating dental
prosthesis that more correctly match the colors/regions of adjacent
teeth. Additionally, in certain embodiments, such data images are
used in conjunction with smile analysis software to further aid in
the prosthesis preparation.
[0198] In a further refinement to the foregoing embodiment,
computer 384 preferably has included therein, or coupled thereto, a
modem. With such a modem capability (which may be hardware or
software), computer 384 may couple data to remote computer 386 over
telecommunication channel 388. For example, remote computer 386 may
be located at a dental laboratory remotely located. Video images
captured using intraoral camera 382 and color/optical data
collected using intraoral reflectometer may be transmitted to a
dental technician (for example) at the remote location, who may use
such images and data to construct dental prosthesis. Additionally,
computer 384 and remote computer 386 may be equipped with an
internal or external video teleconference capability, thereby
enabling a dentist and a dental technician or ceramist, etc., to
have a live video or audio teleconference while viewing such images
and/or data.
[0199] For example, a live teleconference could take place, whereby
the dental technician or ceramist views video images captured using
intraoral camera 383, and after viewing images of the patient's
teeth and facial features and complexion, etc., instruct the
dentist as to which areas of the patient's teeth are recommended
for measurement using intraoral reflectometer 380. Such interaction
between the dentist and dental technician or ceramist may occur
with or without postureization as previously described. Such
interaction may be especially desirable at, for example, a try-in
phase of a dental prosthesis, when minor changes or subtle
characterizations may be needed in order to modify the prosthesis
for optimum esthetic results.
[0200] A still further refinement may be understood with reference
to FIG. 26. As illustrated in FIG. 26, color calibration chart 404
could be utilized in combination with various elements of the
previously described embodiments, including intraoral camera 382.
Color calibration chart 404 may provide a chart of known color
values, which may be employed, for example, in the video image to
further enhance correct skin tones of patient 402 in the displayed
video image. As the patient's gingival tissue, complexion and
facial features, etc., may influence the final esthetic results of
a dental prosthesis, such a color calibration chart may be
desirably utilized to provide better esthetic results.
[0201] As an additional example, such a color calibration chart may
be utilized by computer 384 and/or 386 to "calibrate" the color
data within a captured image to true or known color values. For
example, color calibration chart 404 may include one or more
orientation markings 406, which may enable computers 384 and/or 386
to find and position color calibration chart 404 within a video
frame. Thereafter, computers 384 and/or 386 may then compare
"known" color data values from color calibration chart (data
indicative of the colors within color calibration chart 404 and
their position relative to orientation mark or markings 406 are
stored within computers 384 and/or 386, such as in a lookup table,
etc.) with the colors captured within the video image at positions
corresponding to the various colors of color calibration chart 404.
Based on such comparisons, computers 384 and/or 386 may color
adjust the video image in order to bring about a closer
correspondence between the colors of the video image and known or
true colors from color calibration chart 404.
[0202] In certain embodiments, such color adjusted video data may
be used in the prosthesis preparation process, such as to color
adjust the video image (whether or not postureized) in conjunction
with color/optical data collected using intraoral reflectometer 380
(for example, as described above or using data from intraoral
reflectometer 380 to further color adjust portions of the video
image), or to add subtle characterizations or modifications to a
dental prosthesis, or to even prepare a dental prosthesis, etc.
While not believed to be as accurate, etc. as color/optical data
collected using intraoral reflectometer 380, such color adjusted
video data may be adequate in certain applications, environments,
situations, etc., and such color adjusted video data may be
utilized in a similar manner to color data taken by a device such
as intraoral reflectometer 380, including, for example, prosthesis
preparation, patient data collection and storage, materials
preparation, such as described elsewhere herein.
[0203] It should be further noted that color calibration chart 404
may be specifically adapted (size, form and constituent materials,
etc.) to be positioned inside of the patient's mouth to be placed
near the tooth or teeth being examined, so as to be subject to the
same or nearly the same ambient lighting and environmental
conditions, etc., as is the tooth or teeth being examined. It also
should further be noted that the utilization of color calibration
chart 404 to color correct video image data with a computer as
provided herein also may be adapted to be used in other fields,
such as medical, industrial, etc., although its novel and
advantageous use in the field of dentistry as described herein is
of particular note and emphasis herein.
[0204] FIG. 27 illustrates a further embodiment of the present
invention, in which an intraoral reflectometer in accordance with
the present invention may be adapted to be mounted on, or removably
affixed to, a dental chair. An exemplary dental chair arrangement
in accordance with the present invention includes dental chair 410
is mounted on base 412, and may include typical accompaniments for
such chairs, such as foot control 414, hose(s) 416 (for suction or
water, etc.), cuspidor and water supply 420 and light 418. A
preferably movable arm 422 extends out from support 428 in order to
provide a conveniently locatable support 430 on which various
dental instruments 424 are mounted or affixed in a removable
manner. Bracket table 426 also may be included, on which a dentist
may position other instruments or materials. In accordance with
this embodiment, however, instruments 424 include an intraoral
reflectometer in accordance with the present invention, which is
conveniently positioned and removably mounted/affixed on support
430, so that color/optical measurements, data collection and
storage and prosthesis preparation may be conveniently carried out
by the dentist. As opposed to large and bulky prior art
instruments, the present invention enables an intraoral
reflectometer for collecting color/optical data, in some
embodiments combined or utilized with an intraoral camera as
described elsewhere herein, which may be readily adapted to be
positioned in a convenient location on a dental chair. Such a
dental chair also may be readily adapted to hold other instruments,
such as intraoral cameras, combined intraoral camera/reflectors,
drills, lights, etc.
[0205] With the foregoing as background, various additional
preferred embodiments utilizing variable aperture receivers in
order to measure, for example, the degree of gloss of the surface
will now be described with references to FIGS. 28A to 30B. Various
of the electronics and spectrophotometer/reflectometer implements
described above will be applicable to such preferred
embodiments.
[0206] Referring to FIG. 28A, a probe utilizing variable aperture
receivers will now be described. In FIG. 28A, source A 452
represents a source fiber optic of a small numerical aperture NA,
0.25 for example; receivers B 454 represent receiver fiber optics
of a wider numerical aperture, 0.5 for example; receivers C 456
represent receiver fiber optics of the same numerical aperture as
source A but is shown with a smaller core diameter; and receivers D
458 represent receiver fiber optics of a wider numerical aperture,
0.5 for example.
[0207] One or more of receiver(s) B 454 (in certain embodiments one
receiver B may be utilized, while in other embodiments a plurality
of receivers B are utilized, which may be circularly arranged
around source A, such as 6 or 8 such receivers B) pass to a
spectrometer (see, e.g., FIGS. 1, 3, 11, 12, configured as
appropriate for such preferred embodiments). Receiver(s) B 454 are
used to measure the spectrum of the reflected light. Receivers C
456 and D 458 pass to broad band (wavelength) optical receivers and
are used to correct the measurement made by receiver(s) B.
Receivers C 456 and D 458 are used to correct for and to detect
whether or not the probe is perpendicular to the surface and to
measure/assess the degree of specular versus diffuse reflection
(the coefficient of specular reflection, etc.) and to measure the
translucency of the material/object.
[0208] FIG. 28B illustrates a refinement of the embodiment of FIG.
28A, in which receivers B 454 are replaced by a cylindrical
arrangement of closely packed, fine optical fibers 454A, which
generally surround light source 452 as illustrated. The fibers
forming the cylindrical arrangement for receivers B 454, are
divided into smaller groups of fibers and are presented, for
example, to light sensors 8 shown in FIG. 1. The number of groups
of fibers is determined by the number of light sensors.
Alternately, the entire bundle of receiver fibers B 454 is
presented to a spectrometer such as a diffraction grating
spectrometer of conventional design. As previously described,
receivers C 456 and D 458 may be arranged on the periphery thereof.
In certain embodiments, receivers C and D may also consist of
bundles of closely packed, fine optical fibers. In other
embodiments they consist of single fiber optics.
[0209] The assessment of translucency in accordance with
embodiments of the present invention have already been described.
It should be noted, however, that in accordance with the preferred
embodiment both the light reflected from the surface of the
material/object (i.e., the peaking intensity) and its associated
spectrum and the spectrum of the light when it is in contact with
the surface of the material/object may be measured/assessed. The
two spectrums typically will differ in amplitude (the intensity or
luminance typically will be greater above the surface than in
contact with the surface) and the spectrums for certain materials
may differ in chrominance (i.e., the structure of the spectrum) as
well.
[0210] When a probe in accordance with such embodiments measures
the peaking intensity, it in general is measuring both the light
reflected from the surface and light that penetrates the surface,
gets bulk scattered within the material and re-emerges from the
material (e.g., the result of translucency). When the probe is in
contact with the surface (e.g., less than the critical height), no
light reflecting from the surface can be detected by the receiver
fiber optics, and thus any light detected by the receivers is a
result of the translucency of the material and its spectrum is the
result of scattering within the bulk of the material. The
"reflected spectrum" and the "bulk spectrum" in general may be
different for different materials, and assessments of such
reflected and bulk spectrum provide additional parameters for
measuring, assessing and/or characterizing materials, surfaces,
objects, teeth, etc., and provide new mechanisms to distinguish
translucent and other types of materials.
[0211] In accordance with preferred embodiments of the present
invention, an assessment or measurement of the degree of gloss (or
specular reflection) may be made. For understanding thereof,
reference is made to FIGS. 29 to 30B.
[0212] Referring to FIG. 29, consider two fiber optics, source
fiber optic 460 and receiver fiber optic 462, arranged
perpendicular to a specular surface as illustrated. The light
reflecting from a purely specular surface will be reflected in the
form of a cone. As long as the numerical aperture of the receiver
fiber optic is greater than or equal to the numerical aperture of
the source fiber optic, all the light reflected from the surface
that strikes the receiver fiber optic will be within the receiver
fiber optic's acceptance cone and will be detected. In general, it
does not matter what the numerical aperture of the receiver fiber
optic is, so long as it is greater than or equal to the numerical
aperture of the source fiber optic. When the fiber optic pair is
far from the surface, receiver fiber optic 462 is fully
illuminated. Eventually, as the pair approaches surface 464,
receiver fiber optic 462 is only partially illuminated. Eventually,
at heights less than or equal to the critical height h.sub.c
receiver fiber optic 462 will not be illuminated. In general, such
as for purely specular surfaces, it should be noted that the
critical height is a function of the numerical aperture of source
fiber optic 460, and is not a function of the numerical aperture of
the receiver.
[0213] Referring now to FIGS. 30A and 30B, consider two fiber
optics (source 460 and receiver 462) perpendicular to diffuse
surface 464A as illustrated in FIG. 30A (FIG. 30B depicts mixed
specular/diffuse surface 464B and area of intersection 466B).
Source fiber optic 460 illuminates circular area 466A on surface
464A, and the light is reflected from surface 464A. The light,
however, will be reflected at all angles, unlike a specular surface
where the light will only be reflected in the form of a cone.
Receiver fiber optic 462 in general is always illuminated at all
heights, although it can only propagate and detect light that
strikes its surface at an angle less than or equal to its
acceptance angle. Thus, when the fiber optic pair is less than the
critical height, receiver fiber optic 462 detects no light. As the
height increases above the critical height, receiver fiber optic
462 starts to detect light that originates from the area of
intersection of the source and receiver cones as illustrated.
Although light may be incident upon receiver fiber optic 462 from
other areas of the illuminated circle, it is not detected because
it is greater than the acceptance angle of the receiver fiber.
[0214] As the numerical aperture of receiver fiber optic 462
increases, the intensity detected by receiver fiber optic 462 will
increase for diffuse surfaces, unlike a specular surface where the
received intensity is not a function of receiver fiber optic
numerical aperture. Thus, for a probe constructed with a plurality
of receiver fiber optics with different numerical apertures, as in
preferred embodiments of the present invention, if the surface is a
highly glossy surface, both receivers (see, e.g., receivers 456 and
458 of FIG. 28A, will measure the same light intensity. As the
surface becomes increasingly diffuse, however receiver D 458 will
have a greater intensity than receiver C 456. The ratio of the two
intensities from receivers C/D is a measure of, or correlates to,
the degree of specular reflection of the material, and may be
directly or indirectly used to quantify the "glossiness" of the
surface. Additionally, it should be noted that generally receiver C
456 (preferably having the same numerical aperture as source fiber
optic A 452) measures principally the specular reflected component.
Receiver D 458, on the other hand, generally measures both diffuse
and specular components. As will be appreciated by those skilled in
the art, such probes and methods utilizing receivers of
different/varying numerical apertures may be advantageously
utilized, with or without additional optical characteristic
determinations as described elsewhere herein, to further quantify
materials such as teeth or other objects.
[0215] Referring now to FIG. 31A, additional preferred embodiments
will be described. The embodiment of FIG. 31A utilizes very narrow
numerical aperture, non-parallel fiber optic receivers 472 and very
narrow numerical aperture source fiber optic 470 or utilizes other
optical elements to create collimated or nearly collimated source
and receiver elements. Central source fiber optic 470 is a narrow
numerical aperture fiber optic and receiver fiber optics 472 as
illustrated (preferably more than two such receivers are utilized
in such embodiments) are also narrow fiber optics. Other receiver
fiber optics may be wide numerical aperture fiber optics (e.g.,
receivers such as receivers 458 of FIG. 28A). As illustrated,
receiver fiber optics 472 of such embodiments are at an angle with
respect to source fiber optic 470, with the numerical aperture of
the receiver fiber optics selected such that, when the received
intensity peaks as the probe is lowered to the surface, the
receiver fiber optics' acceptance cones intersect with the entire
circular area illuminated by the source fiber optic, or at least
with a substantial portion of the area illuminated by the source.
Thus, the receivers generally are measuring the same central spot
illuminated by the source fiber optic.
[0216] A particular aspect of such embodiments is that a specular
excluded probe/measurement technique may be provided. In general,
the spectrally reflected light is not incident upon the receiver
fiber optics, and thus the probe is only sensitive to diffuse
light. Such embodiments may be useful for coupling reflected light
to a multi-band spectrometer (such as described previously) or to
more wide band sensors. Additionally, such embodiments may be
useful as a part of a probe/measurement technique utilizing both
specular included and specular excluded sensors. An illustrative
arrangement utilizing such an arrangement is shown in FIG. 31B. In
FIG. 31B, element 470 may consist of a source fiber optic, or
alternatively may consist of all or part of the elements shown in
cross-section in FIG. 28A or 28B. Still alternatively, non-parallel
receiver fiber optics 472 may be parallel along their length but
have a machined, polished, or other finished or other bent surface
on the end thereof in order to exclude all, or a substantial or
significant portion, of the specularly reflected light. In other
embodiments, receiver fiber optics 472 may contain optical elements
which exclude specularly reflected light. An additional aspect of
embodiments of the present invention is that they may be more fully
integrated with an intraoral camera.
[0217] Referring now to FIGS. 32 to 34, various of such embodiments
will be described for illustrative purposes. In such embodiments,
optical characteristic measurement implements such as previously
described may be more closely integrated with an intraoral camera,
including common chassis 480, common cord or cable 482, and common
probe 484. In one such alternative preferred embodiment, camera
optics 486 are positioned adjacent to spectrometer optics 488 near
the end of probe 484, such as illustrated in FIG. 33. Spectrometer
optics 488 may incorporate, for example, elements of color and
other optical characteristics measuring embodiments described
elsewhere herein, such as shown in FIGS. 1-3, 9-10B, 11-12, 20-21,
28A, 28B and 31A and 31B. In another embodiment, camera optics and
lamp/light source 490 is positioned near the end of probe 484,
around which are positioned a plurality of light receivers 492.
Camera optics and lamp/light source 490 provide illumination and
optics for the camera sensing element and a light source for making
color/optical characteristics in accordance with techniques
described elsewhere herein. It should be noted that light receivers
492 are shown as a single ring for illustrative purposes, although
in other embodiments light receivers such as described elsewhere
herein (such as in the above-listed embodiments including multiple
rings/groups, etc.) may be utilized in an analogous manner.
Principles of such camera optics generally are known in the
borescope or endoscopes fields.
[0218] With respect to such embodiments, one instrument may be
utilized for both intraoral camera uses and for quantifying the
optical properties of teeth. The intraoral camera may be utilized
for showing patients the general state of the tooth, teeth or other
dental health, or for measuring certain properties of teeth or
dental structure such as size and esthetics or for color
postureization as previously described. The optical characteristic
measuring implement may then measure the optical properties of the
teeth such as previously described herein. In certain embodiments,
such as illustrated in FIGS. 33 and 34, a protective shield is
placed over the camera for intraoral use in a conventional manner,
and the protective shield is removed and a specialized tip is
inserted into spectrometer optics 488 or over camera optics and
lamp/light source 490 and light receivers 492 (such tips may be as
discussed in connection with FIGS. 23A-23C, with a suitable
securing mechanism) for infection control, thereby facilitating
measuring and quantifying the optical properties. In other
embodiments a common protective shield (preferably thin and tightly
fitted, and optically transparent, such as are known for intraoral
cameras) that covers both the camera portion and spectrometer
portion are utilized.
[0219] Based on the foregoing embodiments, with which translucency
and gloss may be measured or assessed, further aspects of the
present invention will be described. As previously discussed, when
light strikes an object, it may be reflected from the surface,
absorbed by the bulk of the material, or it may penetrate into the
material and either be emitted from the surface or pass entirely
through the material (i.e., the result of translucency). Light
reflected from the surface may be either reflected specularly
(i.e., the angle of reflection equals the angle of incidence), or
it may be reflected diffusely (i.e., light may be reflected at any
angle). When light is reflected from a specular surface, the
reflected light tends to be concentrated. When it is reflected from
a diffuse surface, the light tends to be distributed over an entire
solid hemisphere (assuming the surface is planar) (see, e.g., FIGS.
29-30B). Accordingly, if the receivers of such embodiments measure
only diffusely reflected light, the light spectrum (integrated
spectrum or gray scale) will be less than an instrument that
measures both the specular and diffusely reflected light.
Instruments that measure both the specular and diffuse components
may be referred to as "specular included" instruments, while those
that measure only the diffuse component may be referred to as
"specular excluded."
[0220] An instrument that can distinguish and quantify the degree
of gloss or the ratio of specular to diffusely reflected light,
such as with embodiments previously described, may be utilized in
accordance with the present invention to correct and/or normalize a
measured color spectrum to that of a standardized surface of the
same color, such as a purely diffuse or Lambertian surface. As will
be apparent to one of skill in the art, this may be done, for
example, by utilizing the gloss measurement to reduce the value or
luminance of the color spectrum (the overall intensity of the
spectrum) to that of the perfectly diffuse material.
[0221] A material that is translucent, on the other hand, tends to
lower the intensity of the color spectrum of light reflected from
the surface of the material. Thus, when measuring the color of a
translucent material, the measured spectrum may appear darker than
a similar colored material that is opaque. With translucency
measurements made as previously described, such translucency
measurements may be used to adjust the measured color spectrum to
that of a similar colored material that is opaque. As will be
understood, in accordance with the present invention the measured
color spectrum may be adjusted, corrected or normalized based on
such gloss and/or translucency data, with the resulting data
utilized, for example, for prosthesis preparation or other
industrial utilization as described elsewhere herein.
[0222] Additional aspects of the present invention relating to the
output of optical properties to a dental laboratory for prosthesis
preparation will now be described. There are many methods for
quantifying color, including CIELab notation, Munsell notation,
shade tab values, etc. Typically, the color of a tooth is reported
by a dentist to the lab in the form of a shade tab value. The
nomenclature of the shade tab or its value is an arbitrary number
assigned to a particular standardized shade guide. Dentists
typically obtain the shade tabs from shade tab suppliers. The labs
utilize the shade tabs values in porcelain recipes to obtain the
final color of the dental prosthesis.
[0223] Unfortunately, however, there are variances in the color of
shade tabs, and there are variances in the color of batches of
dental prosthesis ceramics or other materials. Thus, there are
variances in the ceramics/material recipes to obtain a final color
of a tooth resulting in a prosthesis that does not match the
neighboring teeth.
[0224] In accordance with the present invention, such problems may
be addressed as follows. A dental lab may receive a new batch of
ceramic materials and produce a test batch of materials covering
desired color, translucency and/or gloss range(s). The test
materials may then be measured, with values assigned to the test
materials. The values and associated color, translucency and gloss
and other optical properties may then be saved and stored,
including into the dental instruments that the lab services (such
as by modem download). Thereafter, when a dentist measures the
optical properties of a patient's tooth, the output values for the
optical properties may be reported to the lab in a formula that is
directly related, or more desirably correlated, to the materials
that the lab will utilize in order to prepare the prosthesis.
Additionally, such functionality may enable the use of "virtual
shade guides" or other data for customizing or configuring the
instrument for the particular application.
[0225] Still other aspects of the present invention will be
described with reference to FIGS. 35 and 36, which illustrate a
cordless embodiment of the present invention. Cordless unit 500
includes a housing on which is mounted display 502 for display of
color/optical property data or status or other information. Keypad
504 is provided to input various commands or information. Unit 500
also may be provided with control switch 510 for initiating
measurements or the like, along with speaker 512 for audio feedback
(such as previously described), wireless infrared serial
transceiver for wireless data transmission such as to an
intelligent charging stand (as hereinafter described) and/or to a
host computer or the like, battery compartment 516, serial port
socket 518 (for conventional serial communications to an
intelligent charging stand and/or host computer, and/or battery
recharging port 520. Unit 500 includes probe 506, which in
preferred embodiments may include removable tip 508 (such as
previously described). Of course, unit 500 may contain elements of
the various embodiments as previously described herein.
[0226] Charging stand 526 preferably includes socket/holder 532 for
holding unit 500 while it is being recharged, and preferably
includes a socket to connect to wired serial port 518, wireless IR
serial transceiver 530, wired serial port 524 (such as an RS232
port) for connection to a host computer (such as previously
described), power cable 522 for providing external power to the
system, and lamps 528 showing the charging state of the battery
and/or other status information or the like.
[0227] The system battery may be charged in charging stand 526 in a
conventional manner. A charging indicator (such as lamps 528) may
be used to provide an indication of the state of the internal
battery. Unit 500 may be removed from the stand, and an optical
measurement may be made by the dentist. If the dentist chooses, the
optical measurement may be read from display 502, and a
prescription may be handwritten or otherwise prepared by the
dentist. Alternately, the color/optical characteristics data may be
transmitted by wireless IR transceiver 514 (or other cordless
system such as RF) to a wireless transceiver, such as transceiver
530 of charging stand 526. The prescription may then be
electronically created based upon the color/optical characteristics
data. The electronic prescription may be sent from serial port 524
to a computer or modem or other communications channel to the
dental laboratory.
[0228] With reference to FIGS. 37A and 37B, additional aspects of
the present invention will be discussed.
[0229] As is known, human teeth consist of an inner, generally
opaque, dentin layer, and an outer, generally translucent, enamel
layer. As previously discussed, light that is incident on a tooth
generally can be affected by the tooth in three ways. First, the
light can be reflected from the outer surface of the tooth, either
diffusely or specularly. Second, the light can be internally
scattered and absorbed by the tooth structures. Third, the light
can be internally scattered and transmitted through the tooth
structures and re-emerge from the surface of the tooth.
Traditionally, it was difficult, if not impossible, to distinguish
light reflected from the surface of the tooth, whether specularly
or diffusely, from light that has penetrated the tooth, been
scattered internally and re-emitted from the tooth. In accordance
with the present invention, however, a differentiation may be made
between light that is reflected from the surface of the tooth and
light that is internally scattered and re-emitted from the
tooth.
[0230] As previously described, a critical height h.sub.c occurs
when a pair of fiber optics serve to illuminate a surface or object
and receive light reflected from the surface or object. When the
probe's distance from the tooth's surface is greater than the
critical height h.sub.c the receiver fiber optic is receiving light
that is both reflected from the tooth's surface and light that is
internally scattered and re-emitted by the tooth. When the distance
of the probe is less than the critical height h.sub.c, light that
is reflected from the surface of the tooth no longer can be
received by the received fiber optic. In general, the only light
that can be accepted by the receiver fiber optic is light that has
penetrated enamel layer 540 and is re-emitted by the tooth (in
cases where the object is a tooth).
[0231] Most of the internal light reflection and absorption within
a tooth occurs at enamel-dentin interface or junction (DEJ) 542,
which in general separates enamel layer 540 from dentin 544. In
accordance with the present invention, an apparatus and method may
be provided for quantifying optical properties of such sub-surface
structures, such as the color of DEJ 542, with or without
comparison with data previously taken in order to facilitate the
assessment or prediction of such structures.
[0232] Critical height h.sub.c of the fiber optic probe such as
previously described is a function of the fiber's numerical
aperture and the separation between the fibers. Thus, the critical
height h.sub.c of the probe can be optimized based on the
particular application. In addition, a probe may be constructed
with multiple rings of receive fiber optics and/or with multiple
numerical aperture receiving fiber optics, thereby facilitating
assessment, etc., of enamel thickness, surface gloss, tooth
morphology etc.
[0233] It is widely known that the thickness of the enamel layer of
a tooth varies from the incisal edge to the cervical portion of the
tooth crown, and from the middle of the tooth to the mesial and
distal edges of the tooth (see FIGS. 37A and 37B, etc.). By
utilizing multiple rings of receiver fiber optics, a measurement of
the approximate thickness of the enamel layer may be made based on
a comparison of the peak intensity above the tooth surface and a
measurement in contact with the tooth surface. A probe with
multiple critical heights will give different intensity levels when
in contact with the tooth surface, thereby producing data that may
be indicative of the degree of internal scattering and enamel
thickness or tooth morphology at the point of contact, etc.
[0234] Accordingly, in accordance with the present invention, the
color or other optical characteristics of a sub-surface structure,
such as DEJ 542 of a tooth, may be assessed or quantified in a
manner that is in general independent of the optical
characteristics of the surface of the tooth, and do so
non-invasively, and do so in a manner that may also assess the
thickness of the outer layer, such as enamel layer 540.
[0235] Additionally, and to emphasize the wide utility and
variability of various of the inventive concepts and techniques
disclosed herein, it should be apparent to those skilled in the art
in view of the disclosures herein that the apparatus and
methodology may be utilized to measure the optical properties of
objects/teeth using other optical focusing and gathering elements,
in addition to the fiber optics employed in preferred embodiments
herein. For example, lenses or mirrors or other optical elements
may also be utilized to construct both the light source element and
the light receiver element. A flashlight or other commonly
available light source, as particular examples, may be utilized as
the light source element, and a common telescope with a
photoreceiver may be utilized as the receiver element in a large
scale embodiment of the invention. Such refinements utilizing
teachings provided herein are expressly within the scope of the
present invention.
[0236] As will be apparent to those skilled in the art, certain
refinements may be made in accordance with the present invention.
For example, a central light source fiber optic is utilized in
certain preferred embodiments, but other light source arrangements
(such as a plurality of light source fibers, etc.). In addition,
lookup tables are utilized for various aspects of the present
invention, but polynomial type calculations could similarly be
employed. Thus, although various preferred embodiments of the
present invention have been disclosed for illustrative purposes,
those skilled in the art will appreciate that various
modifications, additions and/or substitutions are possible without
departing from the scope and spirit of the present invention as
disclosed in the claims. In addition, while various embodiments
utilize light principally in the visible light spectrum, the
present invention is not necessarily limited to all or part of such
visible light spectrum, and may include radiant energy not within
such visible light spectrum.
[0237] With reference to FIG. 5A, the intensity measured by a
single receiver fiber is shown as a function of time as a source
fiber optic and a receiver fiber optic pair are moved into contact
with an object and are moved away from the object. FIG. 5A
illustrates the intensity as a function of time, however as will be
apparent to one skilled in the art, the intensity detected by the
receiver fiber can also be measured and plotted as a function of
height. A given fiber optic pair of source and receiver fiber
optics, perpendicular to a surface (or at least at a fixed angle
relative to a surface) will exhibit a certain intensity vs. height
relationship. That relationship generally is consistent for certain
materials of consistent gloss, color and translucency. The
mathematical intensity vs. height relationship for certain source
and receiver fiber optic pairs can be calculated or measured and
stored as a look up table value or as a polynomial or other
mathematical relationship. What is important to note is that there
is an intensity peak that is a function of the gloss, translucency
and color of the object being measured. For similar materials, the
intensity value at a given height varies dependent upon color,
although the shape of the intensity vs. height curve is largely
independent of color. Thus, as will be apparent to one skilled in
the art, the present invention may also serve as a proximity
sensor, determining height from the intensity measurements. The
instrument is calibrated by moving it towards the object until the
peaking intensity is detected. While the instrument moves towards
the object, the light intensities are rapidly measured and saved in
memory such as RAM 10 shown in FIG. 1. From the value of the
measured peaking intensity (utilized to normalize the intensity vs.
height relationship of the fiber pair) the proximity sensor can be
calibrated. Thereafter, the present invention may be utilized to
measure the height of the fiber optic pair from the surface of the
object without contacting the object.
[0238] The present invention may find application in a wide range
of industrial activities. Certain applications of the present
invention include, but are not limited to, measuring the optical
properties of teeth and utilizing the measurements as part of a
patient data base and utilizing the measurements for dental
prosthesis preparation.
[0239] Another application of the present invention is its use in
dermatology in quantifying the optical properties including color
of skin and other tissues and saving the measurements as part of a
patient data base record and utilizing the measurements made over a
period of time for diagnostic purposes.
[0240] Yet another application of the present invention is in the
food preparation industry where the color and other optical
properties of certain foods that are affected by the preparation
process are measured and monitored with the disclosed invention and
are utilized to determine whether or not the food meets certain
acceptance criteria and where the measurements may be also utilized
as part of a control and feed back process whereby the food is
further processed until it is either accepted or rejected.
Similarly, in automated food processing, such as for vegetables or
fruit, measurements may be taken and an assessment or prediction of
the condition of the vegetable or fruit made, such as ripeness.
[0241] Yet another application of the present invention is to
measure the color and optical properties of objects newly painted
as part of a control process. For example, paint may be applied to
the object, with the object then measured to determine if a
suitable amount or type of paint has been applied, perhaps with the
process repeated until a measurement corresponding to a desired
surface condition is obtained, etc.
[0242] Yet another application of the present invention is to
measure the optical properties of newly painted objects over a
period of time to discern if the paint has cured or dried.
Similarly, such an object may be measured to determine if
additional gloss coatings, surface texture factors or fluorescence
factors, etc., should be added to achieve a more optimum or desired
object.
[0243] Yet another application of the present invention is in an
industrial or other control system, where items are color coded or
have color or gloss or translucency or combinations of optical
properties that identify the objects and where the optical
properties are measured utilizing the disclosed invention and are
sorted according to their optical properties. In general, the
present invention may be utilized to measure the optical properties
of objects in an industrial process flow, and then compare such
measurements with previously stored data in order to sort,
categorize, or control the direction of movement of the object in
the industrial process.
[0244] Yet another application of the present invention is to place
color coded or gloss coated or translucent tags or stickers on
objects that serve as inventory control or routing control or other
types of identification of objects in industrial processes.
[0245] Yet another application of the present invention is part of
the printing process to measure and control the color or other
optical properties of inks or dies imprinted on materials. In such
embodiments, implements as described herein may be integrated into
the printer or printing equipment, or used as a separate
implement.
[0246] Yet another application of the present invention is part of
the photographic process to measure, monitor and control the
optical properties of the photographic process. In such
embodiments, implements as described herein may be integrated into
the camera or other photographic instrument, or used as a separate
implement.
[0247] Yet another application of the present invention is to
measure the distance to the surface of objects without being placed
into contact with the object.
[0248] The present invention may be used in an industrial process
in which coatings or material are added to or removed from an
object. The object may be measured, and coatings or materials added
or removed, with the object re-measured and the process repeated
until a desired object or other acceptance criteria are satisfied.
In such processes, comparisons with previously stored data may be
used to assess whether the desired object is obtained or the
acceptance criteria satisfied, etc.
[0249] In yet another application, the present invention is
utilized in the restoration of paintings or other painted objects,
such as art works, automobiles or other objects for which all or
part may need to be painted, with the applied paint matching
certain existing paint or other criteria. The present invention may
be used to characterize whether paint to be applied will match the
existing paint, etc. In such processes, comparisons with previously
stored data may be used to assess whether the desired paint match
will be obtained, etc.
[0250] In general, the present invention may find application in
any industrial process in which an object or material may be
measured for surface and/or subsurface optical characteristics,
with the condition or status of such object or material assessed or
predicted based on such measurements, possibly including
comparisons with previously stored data as previously described,
etc. Additionally, and to emphasize the wide utility and
variability of various of the inventive concepts and techniques
disclosed herein, it should be apparent to those skilled in the art
in view of the disclosures herein that the apparatus and
methodology may be utilized to measure the optical properties of
objects using other optical focusing and gathering elements, in
addition to the fiber optics employed in preferred embodiments
herein. For example, lenses or mirrors or other optical elements
may also be utilized to construct both the light source element and
the light receiver element. A flashlight or other commonly
available light source, as particular examples, may be utilized as
the light source element, and a common telescope with a
photoreceiver may be utilized as the receiver element in a large
scale embodiment of the invention. Such refinements utilizing
teachings provided herein are expressly within the scope of the
present invention.
[0251] In addition to the foregoing embodiments, features,
applications and uses, other embodiments and refinements in
accordance with the present invention will now be described. As
with prior descriptions, descriptions to follow are without being
bound by any particular theory, with the description provided for
illustrative purposes. As before, although certain of the
description to follow makes reference to objects or materials,
within the scope of the various embodiments of the present
invention are dental objects such as teeth. Also as before, teeth
or any other particular objects referenced herein are exemplary
uses, and various embodiments and aspects of the present invention
may be used in other fields of endeavor.
[0252] A variety of devices may be used to measure and quantify the
intensity of light, including, for example, photodiodes, charge
coupled devices, silicon photo detectors, photomultiplier tubes and
the like. In certain applications it is desirable to measure light
intensity over a broad band of light frequencies such as over the
entire visible band. In other applications it is desirable to
measure light intensities over narrow bands such as in spectroscopy
applications. In yet other applications it is desirable to measure
high light intensities such as in photographic light meters. In
still other applications it is desirable to measure low light
intensities such as in abridged spectrometers. Typically when
measuring low light intensities, long sampling periods of the order
of one second or longer are required.
[0253] In accordance with other aspects of the present invention, a
method and apparatus are disclosed that may be used to measure
multiple light inputs rapidly. Such an embodiment preferably
utilizes a photodiode array, such as the TSL230 manufactured by
Texas Instruments, Inc., and a gate array manufactured by Altera
Corporation or Xilinx, Inc. In certain applications, such an
embodiment may be utilized to measure broad band visible and
infra-red light. In other applications, such an embodiment may be
utilized as an abridged spectrometer in which each photodiode array
has a notch filter, such as an interference filter, positioned
above the light sensor.
[0254] The TSL230 consists of 100 silicon photodiodes arranged in a
square 10 by 10 array. The 100 photodiodes serve as an input to an
integrator that produces an output signal of a frequency
proportional to the intensity of light incident upon the array. The
TSL230 has scale and sensitivity inputs allowing the sensitivity
and scale to each be varied by a factor of 100, for a net range of
10.sup.4. The output frequency can vary from a maximum of
approximately 300 k Hz (sensor is saturated) to sub Hz ranges.
Thus, the sensor can detect light inputs ranging over seven orders
of magnitude by varying the sensitivity and/or scale of the sensor
and can detect light ranges of over five orders of magnitude at a
given setting.
[0255] In spectroscopy applications for such embodiments, each
sensor is mounted with an optical filter such as an interference
filter. As is known in the art, interference filters have high
out-of-band rejection and high in-band transmission, and may be
constructed with very narrow band pass properties. As an example,
interference filters may be constructed with band pass ranges of 20
nanometers or less. In accordance with certain aspects of the
present invention, an abridged-type spectrometer may be constructed
with TSL230 (or similar) sensors and interference filters that is
suitable for reflectivity or transmission spectrographic
applications such as measuring the color of objects. In color
determination applications it is not necessary to detect "line"
spectra, but it often is desirable to have high gray scale
resolution, e.g., to be able to resolve the light intensity to 1
part in 1000 or greater.
[0256] Instruments and methods for measuring the optical properties
of materials and objects have been previously described. Such an
instrument may consist of a probe and an abridged spectrometer. The
probe may be moved into contact or near contact with the surface of
the material or object (by movement of the probe or
material/object, etc.), and the spectrum of the light received by
the probe was analyzed as the probe was moved towards the surface.
Since the probe was not stationary, preferably numerous
measurements are taken in succession, with the spectra dynamically
taken and/or analyzed as the probe relatively moves in proximity
with the object.
[0257] One difficulty that results from narrowing the band width of
notch or interference filters is that such narrowing reduces the
light intensity incident upon each sensor. Thus, to measure low
light levels, long sampling times typically are required. In the
case of the TSL230 sensor, as the light level decreases, the output
frequency of the device decreases. Thus, if it is desired to make
200 samples per second with an abridged spectrometer constructed
with notch filters and TSL230s, one needs enough light to cause the
TSL230 output to oscillate at a rate of at least 200 Hz. Since the
maximum range of the sensor is approximately 300 k Hz, the maximum
dynamic range of the sensor is reduced to (300 k Hz)/(200 Hz) or
roughly 1.5.times.10.sup.3. If the light inputs are low, then the
dynamic range is reduced still further.
[0258] FIG. 38 illustrates an abridged visible light range
spectrometer in accordance with another embodiment of the present
invention. This embodiment utilizes TSL230 sensors 616, a light
source or lamp 604, preferably a hot mirror that reflects IR light
with wavelengths above 700 nanometers (not expressly shown in FIG.
38), fiber optic cable assembly consisting of one or more sources
(illustrated by light path 608) providing light to object 606, and
one or more receivers (illustrated by light path 618) receiving
light from object 606, gate array 602 such as an Altera FLEX
10K30.TM. (believed to be a trademark of Altera Corporation), which
is coupled to computer 600 and receives signal inputs from sensors
616 over bus 620. In one preferred embodiment up to fifteen or more
TSL230 sensors are utilized. Each TSL230 sensor 616 has an
interference filter 614 positioned above the sensor, with each
filter preferably having a nominal bandwidth of 20 nanometers (or
other bandwidth suitable for the particular application). Sensors
616 also preferably receive a small and controlled amount of light
(light path 610) directly from light source 604, preferably after
IR filtering. The light source input to sensors 616 serves to bias
sensors 616 to produce an output of at least 200 Hz when no light
is input to sensors 616 from filters 614. Thus, sensors 616 will
always produce an output signal frequency greater than or equal to
the sampling frequency of the system. When input light intensities
are small, the frequency change is small, and when the light input
is large, the frequency change will be large. The scale and
sensitivity of sensors 616 are set (by gate array 602 over control
bus 612, which may be under control of computer 600) to detect the
entire range of light input values. In most cases, particularly in
object color determination, the maximum amount of light input into
any one of sensors 616 is determined by light source 604 and
filters 614 and can be appropriately controlled.
[0259] Gate array 602 serves to measure the output frequency and
period of each of sensors 616 independently. This may be done by
detecting whenever an output changes and both counting the number
of changes per sampling period and storing the value of a high
speed counter in a first register the first time an output changes,
and storing the value in a second register for each subsequent
change. The second register will thus hold the final value of the
timer. Both high to low and low to high transitions preferably are
detected. The output frequency (f) of each sensor is thus:
f = ( N - 1 ) ( P h - P l ) 1 ) ##EQU00001##
where:
[0260] N=Number of transitions in sample period;
[0261] P.sub.l=Initial timer count; and
[0262] P.sub.h=Final timer count.
[0263] The internal high speed timer is reset at the start of each
sampling period ensuring that the condition P.sub.h>P.sub.l is
always true.
[0264] The precision of a system in accordance with such an
embodiment may be determined by the system timer clock frequency.
If P.sub.r is the desired precision and S.sub.r is the sampling
rate, then the frequency of the timer clock is:
f.sub.t=P.sub.rS.sub.r 2)
For example, for a sampling rate of 200 and a precision of
2.sup.16, the timer clock frequency is 200.times.2.sup.16 or 13
MHz.
[0265] If the input light intensities are high, N will be a large
number. If the input light intensities are low, N will be small
(but always greater than 2, with proper light biasing). In either
case, however, P.sub.h-P.sub.l will be a large number and will
always be on the order of 1/2 the precision of the system. Thus, in
accordance with such embodiments, the theoretical precision to
which the light intensities can be measured may be the same for all
sensors, independent of light input intensity. If one sensor has an
output range of 200 to 205 Hz (very low light input), the
intensities of light received by this sensor may be measured to
about the same precision as a sensor with 10,000 times more light
input (range of 200 to 50,200 Hz). This aspect of such embodiments
is very unlike certain conventional light sensors, such as those
utilizing ADCs, analog multiplexers and sample and hold amplifiers,
where the precision of the system is limited to the number of bits
of the ADC available over the input range. To provide for the wide
input range in a system with an ADC, a variable gain sample and
hold amplifier typically is required. It is also difficult for an
ADC to sample to 16 bits accurately.
[0266] With such embodiments of the present invention, the absolute
accuracy generally is limited by the stability of the lamp and
electrical noise, both of which may be reduced and in general are
minimal because of the simplicity of the design and the few
components required on a circuit card. A gate array, which may be
field programmable or the like, typically may readily accommodate
20 or more TSL230 sensors and also provide for an interface to a
computer, microprocessor or microcontroller utilizing the light
data. It also should be noted that, instead of a gate array, such
embodiments may be implemented with high speed RISC processors or
by DSPs or other processing elements.
[0267] It should be noted that the use of light biasing, and other
aspects thereof, also are described elsewhere herein.
[0268] In addition to the foregoing embodiments, features,
applications and uses, still other embodiments and refinements in
accordance with the present invention will now be described.
[0269] Certain objects and materials such as gems and teeth exhibit
reflected light spectrums that are a function of incident light
angle and reflected light angle. Such objects and materials are
sometimes referred to as opalescent materials. In accordance with
other embodiments of the present invention, instruments and
methodologies may be provided for specifically measuring and/or
quantifying the opalescent characteristics of objects and
materials, in addition to characteristics such as color, gloss,
translucency and surface texture, it being understood that
previously described embodiments also may be used to capture
spectral and other data (such as a plurality of spectrums), which
can be compared and/or processed to quantify such opalescent
materials.
[0270] Such a further embodiment of the present invention is
illustrated in FIG. 39. In accordance with this embodiment, light
source 638 provides light coupled through a light path (preferably
light source fiber 636) to probe 630 through optical cable 632.
Light received by the probe (i.e., returned from the object or
material being evaluated) is coupled to spectrometer/light sensors
640 through a suitable light path (preferably one or more light
receiver fibers from optical cable 632). Computer 642 is coupled to
spectrometer/light sensors 640 by way of control/data bus 648.
Computer 642 also is coupled to light source 638 by way of control
line(s) 646, which preferably control the on/off condition of light
source 638, and optionally may provide other control information,
analog or digital signal levels, etc., to light source 638 as may
be desired to optimally control the particular light chosen for
light source 638, and its particular characteristics, and for the
particular application. Light from light source 638 optionally may
be coupled to spectrometer/light sensors 640 by light path 644,
such as for purposes of providing light bias (if required or
desired for the particular spectrometer chosen), or for monitoring
the characteristics of light source 638 (such as drift, temperature
effects and the like).
[0271] Computer 642 may be a conventional computer such as a PC or
microcontroller or other processing device, and preferably is
coupled to a user interface (e.g., display, control switches,
keyboard, etc.), which is generically illustrated in FIG. 39 by
interface 652. Optionally, computer 642 is coupled to other
computing devices, such as may be used for data processing,
manipulation, storage or further display, through interface 650.
Computer 642 preferably includes the typical components such as
(but not limited to) a CPU, random access or other memory,
non-volatile memory/storage for storing program code, and may
include interfaces for the user such as display, audio generators,
keyboard or keypad or touch screen or mouse or other user input
device (which may be through interface 652), and optionally
interfaces to other computers such as parallel or serial interfaces
(which may be through interface 650). Computer 642 interfaces to
spectrometer/light sensors 640 for control of the spectrometer and
overall system and to receive light intensity and light spectrum
data from spectrometer/light sensors 640. In a preferred
embodiment, control/data bus 648 for interfacing to
spectrometer/light sensors 640 is a standard 25 pin bi-directional
parallel port. In certain embodiments, computer 642 may be
separate, standalone and/or detachable from spectrometer/light
sensors 640 and may be a conventional laptop, notebook or other
portable or handheld-type personal computer. In other embodiments,
computer 642 may be an integral part of the system contained in one
or more enclosure(s), and may be an embedded personal computer or
other type of integrated computer. Purposes of computer 642
preferably include controlling light source 638 and
spectrometer/light sensors 640, receiving light intensity and
spectral or other data output from spectrometer/light sensors 640,
analyzing received or other data and determining the optical
properties of the object or material, and displaying or outputting
data to a user or other computing device or data gathering
system.
[0272] In a preferred embodiment, the output end of probe 630 may
be constructed as illustrated in FIG. 40. Numerous other probe
configurations, including probe configurations as described
elsewhere herein, may be used in such embodiments. In accordance
with such preferred embodiments, optical characteristics
determination systems/methods may be obtained that provide for a
broader range of measurement parameters, and, in certain
applications, may be easier to construct. Probe cross section 656
includes central fiber optic 658, which is preferably surrounded by
six perimeter fiber optics 660 and 662. Central fiber optic 658 is
supplied by light from the light source (such as light source 638).
Six perimeter fiber optics 660 and 662 are light receivers and pass
to spectrometer/light sensors 640. In one preferred embodiment, all
seven fiber optics have the same numerical aperture (NA); however,
as disclosed below, the numerical aperture of the light source and
consequently the source fiber optic preferably can be varied. Also,
in certain embodiments the received cone of light from certain of
the receiver fiber optics is also controlled and varied to
effectively vary the NA of certain receivers.
[0273] As illustrated in FIG. 40, central fiber optic 658 (S)
serves as the light source. Fiber optics 660 labeled 1,3,5
preferably are "wide band" fibers and pass to light sensors
(preferably within spectrometer/light sensors 640) that measure
light intensity over an entire spectral range. The other three
light receivers 662 labeled 2,4,6 preferably are "dual" receivers
and pass to both a spectrometer and to "wide band" light sensors
(also preferably within spectrometer/light sensors 640). As
previously described, the probe in conjunction with a spectrometer,
computer, light source and "wide band" light receivers can be used
to measure the color and translucency and surface properties of
teeth and other materials. Also as previously described, the probe
with a combination of NA "wide band" receiver fiber optics can
additionally be utilized to measure the gloss or the degree of
specular versus diffuse light received from a surface.
[0274] FIG. 41A is a diagram of a preferred embodiment of
spectrometer/light sensors 640. In this embodiment, certain optical
fibers from the probe are coupled to wide band light sensors (such
sensors, which may include TSL230 sensors and optics and/or filters
as described elsewhere herein are illustrated as sensors 676 in
FIG. 41A), while other of the optical fibers are coupled to both a
spectrometer, in order to spectrally measure the light received by
the probe, and to wide band light sensors. Fibers 660 (1,3,5)
preferably are coupled to three wide band light sensors (light path
682 of FIG. 41A). Preferably, the light receiving/sensing elements
are Texas Instruments TSL230s, although they may also be photo
diodes, CCDs or other light sensors. Fibers 660 (1,3,5) preferably
are masked by iris 694 to reduce the size of the cone of light
produced by the fiber as illustrated in FIG. 42. Mask or iris 694
serves to limit the NA of the receiver by allowing only light rays
with a maximum angle of a to be received by the receiver light
sensor.
If:
[0275] h height of end of fiber to iris
[0276] r=radius of opening of the iris
[0277] a=radius of the fiber
then : .alpha. = Tan - 1 ( r + a h ) 1 ) ##EQU00002##
Hence, the effective NA of the receiver fiber optic can be reduced
and controlled with iris 694. By utilizing a variable iris or an
iris that is controlled with a servo such as those utilized in
conventional cameras, the NA of the receiver fiber optic can be
controlled by the system and can be varied to best match the object
or material being measured. Referring again to FIG. 42, exemplary
receiver fiber 690 provides light to exemplary light sensor 676
through iris 694. Light rays such as light rays 696A of a certain
limited angle pass through iris 694, while other light rays within
the acceptance angle of fiber 690 (the outer limit of the
acceptance angle is illustrated by dashed line 696 in FIG. 42) but
not within the limited angular range allowed by iris 694 are
blocked, thereby enabling iris 694 to effectively emulate having a
reduced or variable NA light receiver.
[0278] Referring again to FIG. 41A, light source 638 may be coupled
to certain of sensors 676 through light path 674. Light bias, such
as previously described, may be provided from the light source, or
alternatively, from separately provided LED 680, which may couple
light to certain of sensors 676 for providing controllable light
bias to sensors 676 through light conduit 678. Control of LED 680
for providing controllable light bias to certain of sensors 676,
etc., is described elsewhere herein. Light from fibers 662
preferably are coupled (through light path 684 in FIG. 41A) to one
or more diffusing cavities 686 (described in more detail elsewhere
herein), outputs of which are coupled to certain of sensors 676
through light paths/conduits 688 as illustrated. Control of sensors
676, and data output from sensors 676, preferably is achieved by
way of gate array 670, which may be coupled to a computing device
by way of interface 668 (the use of gate array or similar
processing element and the use of such a computer device are
described elsewhere herein).
[0279] The use of diffusing cavities 686 in such embodiments will
now be further described. As illustrated, certain of the light
receivers 662 (2,4,6) may be coupled to one or more diffusing
cavities 686 through light path 684, which may serve to split the
light receivers into, for example, six (or more or fewer) fiber
optics with a diffusing cavity as illustrated in FIGS. 43A, 43B,
and 43C. One of light receivers 662 is the central fiber in
diffusing cavity 686 and is surrounded by six fiber optics 702 as
part of fiber optic bundle 698. Diffusing cavity 686 serves to
remove any radial or angular light distribution patterns that may
be present in receiver fiber optic 662, and also serves to more
evenly illuminate the six surrounding fiber optics. Thus, light
receivers 662 (2,4,6) illustrated in FIG. 40 may each be split into
six (or a different number) fibers resulting in eighteen receivers.
Three of the eighteen fibers, one per diffusing cavity, preferably
pass to wide band sensors which may have iris 694 (see FIG. 42).
The other fifteen fibers preferably pass to a spectrometer system
(such as part of spectrometer/light sensors 640, which may consist
of a plurality of sensors 676, such as previously described). For
the visible band, fifteen fiber optics and interference notch
filters preferably are used to provide a spectral resolution
of:
700 nm - 400 nm 15 = 20 nm . 2 ) ##EQU00003##
A greater or lesser number of fibers and filters may be utilized in
accordance with such embodiments in order to increase or decrease
the spectral resolution of the system/spectrometer.
[0280] In FIGS. 41B and 43C, an alternate embodiment of the present
invention utilizing a different arrangement of diffusing cavity 686
will now be described. In such embodiments, three "dual band"
receivers 662 are all positioned in common fiber optic bundle 698
and one diffusing cavity 686 is utilized. Fiber optic bundle 698
preferably contains three receiver fibers 662 and fifteen
additional fibers 703 for the spectrometer system, although greater
or fewer fibers may be utilized in other arrangements depending on
the number of color sensors in the system. In certain embodiments,
fifteen fiber optics 703 in the bundle may be of different
diameters to increase the efficiency of diffusing cavity 686 and
the cross sectional packing arrangement of the optical fibers in
fiber optic bundle 698. As an example of such preferred fiber
bundle arrangements in accordance with such embodiments, larger
diameter fibers may be utilized for the color filters in the blue
range of the visible spectrum, where the light intensity from a
tungsten-halogen lamp source 638 is significantly less than in the
red region of the visible spectrum.
[0281] As described elsewhere herein, a spectrometer system may be
constructed of Texas Instruments TSL230 light sensors, interference
filters, light biasing elements and a gate array such an Altera
FLEX 10K30 in order to control the light sensors, interface to a
computer via a parallel or other interface and to measure the
frequency and period of the light sensors simultaneously at a high
rate in order to accurately and rapidly measure light spectrums and
light intensities. Although such spectrometer systems are used in
preferred embodiments, other spectrometers such as those utilizing,
for example, CCDs with diffraction gratings are utilized in other
embodiments.
[0282] FIG. 44 illustrates a further refinement of aspects of a
spectrometer-type system in accordance with the present invention.
A fiber optic, such as one of the fifteen fibers from three
diffusing cavities as described earlier, preferably pass to light
sensor 710 (which may be a TSL230 light sensor, as previously
described) through interference filter 708. Interference filters
such as interference filter 708 serve as notch filters passing
light over a narrow bandwidth and rejecting light that is out of
band. The bandwidth of the light transmitted through the filter,
however, is dependent upon the angle of incidence of the light on
the filter, and in general is broadened as the angle of incidence
increases. Since fiber optics produce a cone of light, it has been
determined that it is desirable to collimate the cone to reduce
such bandwidth spreading. As illustrated in FIG. 44, the cone of
light produced by exemplary fiber optic 704 (illustrated by lines
712A) preferably is collimated with first aspheric lens (or fresnel
lens) 706A (illustrated by lines 712B) prior to entering
interference filter 708. Light emitted from filter 708 (illustrated
by lines 712C) is "gathered" by second aspheric lens (or fresnel
lens) 706B to concentrate (illustrated by lines 712D) as much light
as possible on light sensor 710. In accordance with such
embodiments, filters, particularly interference-type filters, may
more optimally be utilized in a manner to reduce such bandwidth
spreading or other undesirable effects.
[0283] Referring again to FIG. 41A (the discussion also is
generally applicable to FIG. 41B), light biasing as previously
described will be discussed in greater detail. As previously
described, in order to rapidly sample TSL230-type sensors, the
sensors may require light biasing. Without light biasing, depending
upon the light intensity presented to the particular sensors, a
TSL230 sensor may not produce an output change pair of transitions
(e.g., high to low and low to high transitions, or low to high and
high to low transitions) during the sampling period, hence a light
intensity measurement may not be possible for that sensor. In
preferred embodiments, the sensing system detects both high to low
and low to high transitions and requires at minimum two transitions
to make a measurement. In other words, such system measures half
periods. For example, assume that as the light intensity on a
particular TSL230 decreases such that its output frequency
decreases from 201 Hz to 199 Hz. At 201 Hz, the output of the
TSL230 transitions with a period of 1/201 sec or every 4.975 ms. At
199 Hz, the output transition period is 1/199 sec or 5.025 ms. If
the sampling rate is 200 samples per second, then the sampling
period is 5.00 ms. Thus, if the TSL230 transitions every 4.975 ms,
the sensing system will always detect either two or three
transitions and will always be able to make an intensity
measurement. At 199 Hz, however, the detection circuitry will
detect either one or two transitions. As a result, during certain
sampling intervals, measurements are possible, while during other
intervals measurements are not possible, thereby resulting in
measurement discontinuities even though the light intensity has not
changed.
[0284] It is desirable to measure light over a broad range of
intensity values at high rates including very low light
intensities. By utilizing light biasing of the TSL230 sensors as
illustrated in FIG. 41A, the minimal output frequency of the
TSL230s can be controlled. The minimal light value preferably is
measured as part of a normalization or calibration procedure as
follows. [0285] 1. The light bias is turned on and allowed to
stabilize. [0286] 2. The probe is placed into a black enclosure. A
"black level" intensity measurement I.sub.b is made and recorded
for each sensor, preferably in a simultaneous manner. [0287] 3. The
light source is turned on and allowed to stabilize. A "white level"
intensity measurement I.sub.w is made and recorded for each sensor,
again preferably in a simultaneous manner, on a "white" standard
such as barium sulfide or on "Spectralon," believed to be a
trademarked product of Labsphere, Inc. The actual intensities
measured by all sensors will vary from the standard values I.sub.s.
Typically in color measurements the standard value I.sub.s is
nominally "100%." [0288] 4. Subsequent light measurements may be
normalized by subtracting the "black level" intensity and by
adjusting the gain from the white level measurement resulting in a
normalized intensity I.sub.N for each sensor as follows:
[0288] I N = I s I w - I b ( I - I b ) 3 ) ##EQU00004##
where I=Intensity measurement and I.sub.N is the normalized or
calibrated intensity measurement. It should be noted that in such
preferred embodiments the normalization is made for each light
sensor, and independent "black level" and "white level" intensities
are saved for each sensor.
[0289] In certain situations, a long time may be required for the
light source and for the light bias source to stabilize. In other
situations, the light source and bias source may drift. In
preferred embodiments, the light source is a 18 W, 3300K halogen
stabilized tungsten filament lamp manufactured by Welch Allyn, Inc.
The light bias preferably is provided by a high intensity LED and a
fiber optic light guide or conduit (see LED 680 and light conduit
678 of FIG. 41A) that passes to each biased sensor of sensors 676.
The intensity of LED 680 preferably is controlled and varied with
high frequency pulse width modulation, or by analog constant
current controllers. By controlling the intensity of bias LED 680,
the bias light level can be varied to best match the sensor
sampling rate.
[0290] Preferably, one sensor, such as a TSL230 sensor, is provided
to measure the intensity of LED 680 and to correct for intensity
variations of the LED light biasing system. Since LED 680 is
monochromatic, one sensor typically is sufficient to track and
correct for bias LED intensity drift. The LED bias intensity
preferably is measured and recorded when the "black level"
measurement is made. For each subsequent light intensity
measurement, the black level for each sensor is corrected for LED
drift as follows:
I b ( Corrected ) = I b I ( BiasSensor ) I b ( BiasSensor ) 4 )
##EQU00005##
where: I(BiasSensor) is the intensity measured by the bias sensor,
I.sub.b(BiasSensor) is the "black level" intensity measured by the
bias sensor, I.sub.b is the "black level" intensity measured by a
light sensor (other than the bias sensor) and I.sub.b(Corrected) is
the adjusted bias used in equation 4) above.
[0291] Light source drift preferably is measured by a plurality of
light sensors. Since the light source is polychromatic light, its
spectrum may also drift. It is understood that tungsten filament
lamps produce spectrums that are very nearly approximated by the
spectrums of black body radiators and can be represented by the
Planck law for black body radiators.
I ( .lamda. ) = ( 2 .pi. h c .lamda. 3 ) ( 1 k T .lamda. h c - 1 )
5 ) ##EQU00006##
The only variable affecting the intensity of a black body radiator
at any wavelength within the visible band is the temperature (T) of
the source. Thus, a single narrow band light sensor may be utilized
to detect temperature variations of such a source. Additional
factors, however, may affect the spectral output of the lamp, such
as depositing of the filament on the lamp envelope or adjusting the
spectrum of the lamp as described below. In the preferred
embodiment, for more accurate spectral corrections and intensity
variations of the lamp, additional narrow band filters are
utilized. In certain of such preferred embodiments, three band pass
filters and sensors are utilized to measure the spectral shift and
intensity of the lamp in a continuous manner, and such filters and
sensors preferably are further utilized to correct for lamp
spectral and intensity drift.
[0292] FIG. 45 illustrates a preferred embodiment of a light source
used in preferred embodiments of the present invention. Such a
light source preferably consists of halogen tungsten filament lamp
724, with a lens molded into the envelope of the lamp that produces
a concentrated light pattern on an axis parallel to the body of
lamp 724. The use of such a lens in lamp 724 is to concentrate the
light output and to reduce the shadowing of the lamp filament that
may result from lamps with reflectors. Hot mirror 722, which
preferably is a "0.degree. hot mirror," reduces the intensity of IR
light input into the system. In certain embodiments, the hot mirror
may also contain color correction properties, for example, reducing
light intensity for longer (red) wavelengths more than for shorter
(blue) wavelengths. Light output from lamp 724 passes through hot
mirror 722 preferably to tapered glass rod 720. The end of glass
rod 720 nearest lamp 724 preferably has a diameter nominally the
diameter of the envelope of lamp 724. The other end of glass rod
720 preferably is nominally 4 mm, or up to four times or more the
diameter of source fiber optic 714.
[0293] Glass rod 720 serves a number of purposes. First, glass rod
720 serves as a heat shield for fiber optic 714 by allowing fiber
optic 714 to be displaced from lamp 724, with fiber optic 714 being
thermally insulated from lamp 724 by the existence of glass rod
720. Second, glass rod 720 serves to concentrate the light over a
smaller area near fiber optic 714 and to broaden the angular
distribution of light emerging from the narrow end to provide a
distributed light pattern that can uniformly "fill" the NA of
source fiber optic 714. Without tapered glass rod 720, the angular
distribution pattern of light emerging from lamp 724 may not
entirely or evenly fill the acceptance cone of source fiber optic
714. To ensure that source fiber optic 714 is desirably filled with
light without an implement such as glass rod 720 would require
source fiber optic 714 to be very close to lamp 724, thereby
creating a risk that source fiber optic 714 will overheat and
possibly melt.
[0294] Between source fiber optic 714 and glass rod 720 preferably
is iris 718. Iris 718 preferably is utilized to limit the angular
range of light rays entering source fiber optic 714. When iris 718
is fully open, the entire acceptance cone of source fiber optic 714
may be filled. As iris 718 is closed, the cone of light incident
upon source fiber optic 714 is reduced, and hence the angular
distribution of light incident upon fiber optic 714 is reduced. As
iris 718 is reduced further, it is possible to produce a nearly
collimated beam of light incident upon fiber optic 714.
[0295] It is understood that a property of fiber optics whose ends
are highly polished perpendicular to the axis of the fiber optic is
that the angle of light incident on one end of the fiber optic is
preserved as it exits the other end of the fiber optic. As is known
to those skilled in the art, numerous technologies exist for
polishing fiber optic cables. Thus, with a highly polished fiber
optic, by varying the diameter of iris 718, the cone of light
entering source fiber optic 714 can be controlled, and thus the
cone of light emerging from source fiber optic 714 can be
controlled.
[0296] In an alternate embodiment, iris 718 is replaced by disk
730, which preferably includes a pattern of holes positioned near
its perimeter as illustrated in FIGS. 46A and 46B. Preferably, disk
730 is driven with stepping motor 738 through gear 736 and gear
teeth 730A so that disk 730 may be rapidly moved to a desired
position and held it in a stable position in order to make a light
measurement. Stepping motor 738 is controlled by a computer (such
as described elsewhere herein; see, e.g., FIGS. 38 and 39), which
controls disk 730 to rotate about axis 732 and stop in a desired
and controllable position. Thus, such a computer in effect can vary
the NA of the light source synchronously to each measurement. The
procedure preferably progresses as follows.
1. Rotate the disk to the desired aperture. 2. Pause to allow the
disk to stabilize. 3. Measure one light sample. 4. Rotate the disk
to the next desired aperture and repeat the process as
required.
[0297] As illustrated FIG. 46B, the pattern of holes on disk 730
may be round or any other desired shape. Such apertures also may
constitute a pattern of microscopic holes distributed to affect the
light pattern of light or spectrum of light entering the source
fiber. Additionally, the disk may contain filters or diffraction
gratings or the like to affect the spectrum of the light entering
the source fiber. Such holes or apertures also may consist of rings
that produce cones of light where the light rays entering the fiber
are distributed over a narrow or other desired range of angles.
With the disk embodiment of FIGS. 46A and 46B, it is possible to
control the light pattern of source fiber optic 714 effectively
over a wide range of angles.
[0298] Referring again to FIG. 45, light conduit 716 passes light
such as through light path 674 to sensors 676 (see, e.g., FIGS. 41A
and 41B) for measuring the spectral properties of the lamp as
described earlier. If the iris or aperture disk controlling the
distribution of light entering source fiber optic 714 modifies the
spectral properties of the light source, then the resulting
spectrum can be adjusted as described earlier.
[0299] When a pair of fiber optics is utilized as described herein
where one fiber serves as a light source and another fiber serves
as a light receiver, the intensity of light received by the
receiver fiber varies with the height of the pair above the surface
of the object or material and also with the angle of the pair
relative to the surface of the object or material. As described
earlier, in certain preferred embodiments the angle of the probe
relative to the surface may be detected by utilizing three or more
fiber optic receivers having the same receiver NA. After
normalization of the system, if the intensities of the three
receiver fibers (such as fibers 660 (1,3,5) in FIG. 40) are the
same, then this is an indication that the probe is perpendicular to
the surface. If the intensities vary between the three sensors,
then this is an indication that the probe is not perpendicular to
the surface. As a general statement, this phenomenon occurs at all
heights. In general, the intensity variation of the three fibers is
dependent upon the geometry of the three fibers in the probe and is
independent of the color of the material. Thus, as the probe is
tilted towards fiber 1, for example, the intensities measured by
sensors 3 and 5 will be nominally equal, but the intensity measured
by fiber 1 will vary from fibers 3 and 5. As a result, the system
can detect an angular shift towards fiber 1. In preferred
embodiments, by comparing the intensity values of fiber 1 to fibers
3 and 5, a measurement of the angle can be made and the intensity
of fibers 1, 3 and 5 can be corrected by a correction or gain
factor to "adjust" its light measurement to compensate for the
angular shift of the probe. It is thus possible with the probe
arrangement illustrated in FIG. 40 to detect and measure angular
changes.
[0300] Angular changes also will affect the intensities measured by
the other fibers 662 (2,4,6). In a similar manner, the difference
between the "wide band" sensors in fibers 662 (2,4,6) can also be
utilized to further quantify the angle of the probe and can be
utilized to adjust the light intensity measurements. It should be
noted, however, that the intensity shift due to angle of the probe
affects the fibers differently. If sensors 662 (2,4,6) are utilized
in the spectrometer illustrated in FIG. 41A, the intensity
adjustment must be made independently for each fiber and for the
set of six fibers emerging from diffusing cavity 686 illustrated in
FIG. 43A. However, if one diffusing cavity 686 is utilized as
illustrated in FIG. 41B, the angle correction applies to all
sensors supplied by light paths 703 equally. With such an
embodiment as illustrated in FIG. 41B, angle determination and/or
correction may be made in a manner more desirable for some
applications.
[0301] As the probe approaches the surface of an object or material
(the probe may be moved towards the material or the material may be
moved towards the probe), the source fiber illuminates the
object/material. Some light may reflect from the surface of the
object/material, and some light may penetrate the object/material
(if it is translucent or has a translucent layer on its surface)
and re-emerge from the material and may strike the receiver fiber
optic. As described elsewhere herein, the intensity measured by the
receiver exhibits a peaking phenomenon where the light intensity
varies to a maximum value, and then falls until the probe is in
contact with the object/material where it exhibits a minimum. If
the object/material is opaque, then the light intensity at the
minimum is essentially zero. If the object/material is highly
translucent, then the intensity may be near the peaking
intensity.
[0302] Based on such phenomena, in accordance with other aspects of
the present invention, it is possible to quantify the height of the
probe and to adjust for height variations of the probe near the
peaking height by measuring the peaking height intensity of the
"wide band" sensors and comparing the intensity value at other
heights and adjusting the gain of all sensors by the ratio of the
measured intensity to the peaking intensity. If I.sub.p is the peak
intensity of a wide band receiver, and I.sub.m is the intensity
measured when the probe is in contact with the material, and I is
the intensity measured at a height less than the peaking height
then the ratio:
G = I p - I m I - I m 6 ) ##EQU00007##
is the gain adjustment factor. If the gain adjustment factor is
applied to the spectrometer sensors, then the spectrum may be
measured independent of height for a wide range of heights within
the peaking height.
[0303] Reference should now be made to FIGS. 47A and 47B. As a
fiber optic pair (e.g., source fiber optic 742 and receiver fiber
optic 744) approach a material or object 746, material or object
746 is illuminated by source fiber optic 742 (see, e.g., lines 745
of FIG. 47A). The light emitted from source fiber optic 742 may be
controlled as described elsewhere herein. Thus, source fiber optic
742 can be controlled so as to illuminate material or object 746
with nearly collimated light (small incident angles), or source
fiber optic 742 can be controlled to illuminate material or object
746 with wide incident angles, or with a pattern of angles or with
different spectral properties. If source fiber optic 742 is
illuminated with an aperture disk with a slit pattern as
illustrated in FIG. 46B, then source fiber optic 742 may be used to
illuminate material or object 746 with a narrow singular range of
angles.
[0304] Consider source fiber optic 742 and receiver fiber optic 744
with the same NA as illustrated in FIGS. 47A and 47B. The angular
distribution of light provided by source fiber optic 742 is
dependent upon the source fiber only (and the angle of the probe)
and is independent of the height of the fiber from the material. If
the probe is held substantially perpendicular to material or object
746, the angular distribution of light is independent of height.
The area illuminated by source fiber 742, however, is height
dependent and increases with increasing height. Receiver fiber
optic 744 can only receive light that is within its acceptance
angle, thus it can only detect light reflected from the surface
that is reflected from the area of overlap of the two cones
illustrated in FIGS. 47A and 47B.
[0305] FIG. 47A illustrates the fiber pair at the peaking height,
while FIG. 47B illustrates the fiber pair at the critical height.
At the critical height, the only light reflecting from the surface
that can be received by receiver fiber 744 is the source ray 745
and the reflected ray 748 with angle of incidence equal to angle of
reflection, or it can only detect "spectrally" reflected light.
When the probe is at the peaking height, however, the reflected
light rays that can be received by the receiver fiber vary over
both a wider angle of incidence range and wider angle of reflection
range. Thus, at the peaking height, the receiver is detecting a
broad range of incident angle light rays and reflected angle light
rays. By adjusting the spectrum for height shifts as described
above and by detecting the angle of the probe relative to the
surface of the material or object, the reflected or returned
spectrum can be measured over a wide incident angular range and
reflected angular range.
[0306] In general, for opaque surfaces, diffuse or specular, the
height adjusted spectrum will appear constant as the probe
approaches the material or object. In general, for opalescent
materials or objects, i.e., materials with a translucent surface in
which light rays may penetrate the material and be re-emitted, the
height adjusted spectrum will shift as the probe approaches the
material or object. In general, for translucent materials such as
teeth or gem stones, the spectrum will further shift when the probe
is less than the critical height and in contact or near contact
with the material or object.
[0307] As a further refinement to certain aspect of the present
invention, the iris illustrated in FIG. 45 or the aperture disk
illustrated in FIGS. 46A and 46B may be utilized. In one such
embodiment, the NA of source fiber optic 714 is held constant as
the probe approaches the material or object, and light intensity
and spectrum measurements are made and saved in a data queue as
described earlier. When the probe is in contact with the material
or object, the NA of source fiber optic 714 is changed (either from
narrow to wide or from wide to narrow, depending upon the state of
the first set of measurements), and spectral measurements are made
as a function of source NA. The probe is then moved away from the
material and light intensity and spectral measurements are made as
the distance from the probe increases and as the probe passes
through the peaking height. The spectral shift that occurs as a
result of the variance of the source NA and height preferably is
used to quantify the opalescence of the material or object.
[0308] In an alternate embodiment, the aperture disk illustrated in
FIGS. 46A and 46B is rotated by stepping motor 738 synchronously to
measuring the light and spectral data as the probe is moved into
proximity to the material or object or into contact with the
material or object. In another alternate embodiment, the probe is
positioned at a fixed height from the material or in contact with
the material or object and the NA of the source fiber is varied as
light intensity and spectral data are measured. In yet another
alternate embodiment, both the source and receiver fiber NAs are
varied as described earlier, and the resulting spectra are utilized
to quantify the optical properties of the material.
[0309] An alternative embodiment of the present invention for
quantifying the degree of gloss of a material will now be described
with reference to FIGS. 48A and 48B. FIGS. 48A and 48B illustrate
source (742) and receiver (744) fiber pair positioned above a
highly specular surface such as a mirror (FIG. 48A) and above a
diffuse surface (FIG. 48B). The cone of light from source fiber
optic 742 is illustrated by circle 742A, and the acceptance cone of
receiver fiber optic 744 is illustrated by circle 744A, with the
overlap illustrated by area 750. On a specular surface, the only
light that will be received by receiver fiber optic 744 are the
light rays whose angle of reflection equal the angle of incidence,
thus the only light rays striking the surface of receiver 744 are
the light rays striking the small circular area the size of the
diameter of the fiber optics as illustrated by circle 752 in FIG.
48A. As long as receiver fiber optic 744 has an NA greater than
source fiber optic 742, all light incident upon receiver fiber
optic 744 will be accepted. Thus, the angular distribution of
received light rays in receiver fiber optic 744 is limited to a
very narrow range and is dependent upon the height of the fiber
optic pair from the surface.
[0310] Consider FIG. 48B, which illustrates a fiber optic pair
positioned above a diffuse surface. Any light ray incident upon the
area of overlap of the two cones can be received by receiver fiber
optic 744 (provided of course that it is incident upon the receiver
fiber). Thus, for diffuse surfaces, the angular distribution of
light rays received by receiver fiber optic 744 is also height
dependent, but is greater than the angular distribution for a
specular surface. In accordance with such embodiments of the
present invention, such angular distribution variation may be used
to quantify optical properties such as gloss for a particular
material or object.
[0311] A detector in accordance with other embodiments of the
present invention is illustrated in FIG. 49, where single receiver
fiber 758 is positioned above a radial distribution of sensors
(illustrated by sensors 760A and 760B). Two or more sensors may be
utilized, in one or two dimensions, although only two sensors are
illustrated in FIG. 49 for discussion purposes. In the illustrated
embodiment, one sensor (sensor 760B) is positioned corresponding to
the center of fiber 758 and measures angles near zero, and the
other sensor (sensor 760A) is positioned at approximately 1/2 the
acceptance angle of receiver fiber 758. In alternate embodiments,
the sensors may be arranged or configured in a linear array such as
a CCD, or a two dimensional sensor such as a video camera CCD or
MOS sensor. In accordance with aspects of the present invention, by
analyzing the intensity patterns of the sensors, the degree of
gloss of the material may be measured and quantified.
[0312] As the probe is moved towards the material or object, the
angular distribution of light received by receiver fiber 758
changes dependent upon the surface of the material or object as
illustrated in FIGS. 50A and 50B. FIG. 50A illustrates the
intensity pattern for the two sensors for a specular surface, and
FIG. 50B shows the intensity pattern for a diffuse surface.
Specular materials in general will tend to exhibit a peaking
pattern where the peaking intensity of sensor 1 is much larger than
the peaking intensity of sensor 2. For diffuse materials the
peaking intensity of sensor 2 (wide angles) is closer to the
peaking intensity of sensor 1. By quantifying the variation in
peaking intensity the degree of gloss of the material can be
additionally quantified. In addition, in alternative embodiments,
the relative values of the sensors at a time when one or the other
sensors is peaking are captured and further used to quantify the
optical properties of the material or object.
[0313] Various particular preferred embodiments of the present
invention will now be described that relate to detecting and
preventing counterfeiting and the like.
[0314] Numerous negotiable instruments exist that are created
utilizing printing processes or the like. Such negotiable
instruments include currency, bonds, stocks, securities, travelers
checks, checks, credit cards, passports, and other types of
business, legal and/or governmental documents or certificates, etc.
In many cases the printing process is highly refined utilizing
microprint or other forms of printing that are difficult to
reproduce, thereby rendering the instrument, document, or
negotiable item difficult to reproduce or to create. Additionally,
the item may contain a paper or other backing material difficult to
reproduce. In other cases, the item may contain holographs or other
fields making it further difficult to reproduce. In yet other
applications, the item may contain inks that have radioactive
isotopes, or magnetic qualities, or other properties that are
difficult to detect or to reproduce. In yet other applications the
item may have strips of materials or certain pigments imbedded
internally that are identifiable but difficult to reproduce. In
general, numerous methods and methodologies exist or have been
proposed that render certain documents or negotiable instruments
difficult to reproduce. Such processes however, tend to be
inherently difficult to implement, and, indeed, the difficulty in
creating the process is the counterfeiting preventive measure.
[0315] With optical characteristics determinations made in
accordance with the present invention, improved methods of
detecting and preventing counterfeiting may be obtained. In
accordance with the present invention, layers of pigment or other
materials in the printing or similar process may be utilized that
render items difficult to reproduce, but relatively easy to create
and/or detect.
[0316] As previously described, various optical properties of an
object may be measured, assessed or predicted in accordance with
the present invention. Such optical properties include surface
reflection, translucency of surface layers, gloss of the surface
and the spectral properties of semi-translucent layers on the
surface and of the spectral properties of layers below the surface.
Such apparatus and methodologies can be utilized to render printing
or similar processes difficult to reproduce.
[0317] FIGS. 51A to C illustrates instrument 601 (which may be any
of the items previously discussed or other items needing
counterfeit protection, etc.) that includes a number of layers of
pigment or other material. Outer layer or layers (603) generally
are semi-transparent or translucent or semi-translucent. Inner
layer or layers 605 may be opaque or semi-translucent. The layers
are deposited by successively printing pigments (or painting or
other deposition or application, etc.) on substrate 607, which may
be any suitable backing material, such as paper or plastic or other
materials, etc.
[0318] If light is reflected from the surface of instrument 601 it
in general will exhibit certain optical properties which can be
measured by conventional spectrographic or colorimetry techniques.
The spectrum of the reflected light will be principally influenced
by the surface properties of outer layer(s) 603 and to a lesser
degree by inner layer(s) 605 and/or substrate 607, depending upon
the degree of translucency of the various layers, etc. If the
material is illuminated from the rear, in general the spectral
properties of the material will be influenced by all layers of the
material, and in general can be quite different from the spectral
properties of light reflected from the face of the object.
[0319] Preferred embodiments herein provide an instrument and
methodology that can distinguish surface reflection properties of
an item/material from bulk spectral properties of the
item/material, which can be advantageously utilized for
preventing/detecting counterfeiting. In such preferred embodiments,
an instrument or item document includes substrate 607 printed (or
otherwise formed) with inner layer(s) 605 consisting of a
relatively long term (depending upon the particular application)
stable dye or other pigment or material, and also includes outer
layer(s) 603, that preferably consist of a semi-translucent layer
printed or otherwise deposited or from inner layer(s) 605. It
should be noted that such layer formation may be part of the
overall process that forms the instrument or other item, or it may
be separate processes that form layers 603 and 605 in a particular
location or locations 609 on instrument 601. In certain
embodiments, layers 603 and 605 are formed from a fixed or
predetermined position from a location marker also included on
instrument 601. Such location marker may facilitate the measuring
of optical properties of such layers, as will be described, and may
provide a further barrier in that the location of the position
where optical properties are to be assessed may not be known to an
unauthorized person or device, etc.
[0320] Following the printing or other formation processes of
layers 603 and 605 (and drying or curing, etc.), the optical
properties of instrument 601 are quantified including, for example,
the surface spectral properties and the spectral properties of the
inner layer. Such optical properties may be measured at a single or
multiple locations. Such spectral or other optical properties may
be recorded and saved such as in a computer data base for future
reference. To determine if the document or material is genuine, the
spectral properties of instrument 601, and in particular layers 603
and 605, are measured and compared to the previously recorded
measurements. Based on such comparisons, which may include a number
of acceptance criteria (such as delta E values or other such
thresholds or ranges), an assessment or prediction may be made of
whether instrument 601 is genuine or counterfeit.
[0321] In another such embodiment, inner layer(s) 605 may be
printed/formed with different layers of pigments that are changed
from batch to batch or periodically, from time to time. The
particular pigment for particular instruments may be recorded and
stored and may be identified to the particular instruments with a
serial number or other form of identification. The pigments of
inner and outer layers 603 and 605 may be adjusted in order to
insure that the instrument appears to have the same color when
visually inspected or when measured with traditional spectrographic
or colorimetry techniques. Thus, an entire series of instruments,
materials or documents or currency can be printed/formed which
visually appear the same, yet have internal or subsurface
properties that can be quantified utilizing the apparatus and
methodology disclosed elsewhere to uniquely distinguish the
documents.
[0322] In another such embodiment, inner layer(s) 605 are
printed/formed with pattern 611 (see FIG. 51C) such as a pattern
utilized in a bar code. The pigments of the inner and outer layers
are chosen to render the inner bar codes difficult if not
impossible to discern visually by utilizing conventional
spectrographic or colorimetry techniques.
[0323] In yet another embodiment, inner layer(s) 605 are
printed/formed with pattern 611 such as a bar code where the bar
code utilizes not only differences in the widths of the lines of
the bars as a method of storing data in the pattern, but also where
the bars themselves are of different pigments. In such
applications, data for the bar code can be encoded in the bars
themselves and in the color of the bars. If the material is layered
as disclosed above, the bar data is difficult if not impossible to
discern, rendering it difficult if not impossible to reproduce.
With such embodiments, individuals or institutions may create an
"identifier stamp" or the like that uniquely identifies objects,
with the stamp consisting of a color bar code or other spectrally
identifying feature or aspect. This could be combined, for example,
with a visible bar or other code, and with other information or bar
code (or message), etc., that is discernible only with an
instrument such as provided herein. In such embodiments, a
subsurface bar code or spectral identification may be provided,
with or without a visible code, message or data.
[0324] In yet another embodiment, inner layer(s) 605 are
printed/formed with geometric two dimensional patterns that can be
discerned as described herein by scanning the instrument, document
or material, such as on two or more axis. In yet another
embodiment, inner layer(s) 605 are printed/formed in multiple
layers. Certain configurations of the measuring apparatus may be
constructed to principally measure specific layers or thickness' of
layers or spectral properties of layers. Thus, one measurement may
produce one set of optical properties, while another measurement
produces yet another set of optical properties, and so on rendering
the instrument, document or material even more difficult to
reproduce.
[0325] Such embodiments may be applicable to a wide class of
objects. Although the foregoing discussion has focused on documents
or negotiable instruments of paper or plastic such as currency or
checks etc., it is equally applicable as an identification to works
of art or objects or precious items or any material or object than
can accept imprinting or other material preparation. Indeed, the
quality of the printing of the original object need not be highly
controlled either in color or in print quality. Since the imprint
placed on the object is recorded both spectrally and spatially
after the imprinting process (either as linear or multi-axis
measurements) and recorded, it renders the identification mark
difficult to reproduce.
[0326] Additionally, and particularly with respect to objects such
as paintings, sculptures, and the like, it may be possible to
determine optical properties as described herein in one or more
locations, based on the constituent layers of the object (i.e.,
without forming special layers 603, 605, etc.). In general, it may
be possible to optically characterize such objects, with optical
characteristic data stored for later comparisons to determine if
the object is genuine or counterfeit. Still additionally, it may be
possible to use specially formed inner layers that include codes or
other subsurface spectral characteristics that may be measured in
accordance with the present invention, but which would not be
discernible visually or by utilizing conventional spectrographic or
colorimetry techniques. In such embodiments, the outer visible
characteristics may completely mask the subsurface code or spectral
identifier, which may remain hidden except when assessed as
provided herein in order to detect for genuineness, etc.
[0327] As will be apparent to those skilled in the art, certain
refinements may be made in accordance with the present invention.
For example, a central light source fiber optic is utilized in
certain preferred embodiments, but other light source arrangements
(such as a plurality of light source fibers, etc.). In addition,
lookup tables are utilized for various aspects of the present
invention, but polynomial type calculations could similarly be
employed. Thus, although various preferred embodiments of the
present invention have been disclosed for illustrative purposes,
those skilled in the art will appreciate that various
modifications, additions and/or substitutions are possible without
departing from the scope and spirit of the present invention as
disclosed in the claims. In addition, while various embodiments
utilize light principally in the visible light spectrum, the
present invention is not necessarily limited to all or part of such
visible light spectrum, and may include radiant energy not within
such visible light spectrum.
[0328] As described above, in accordance with the present invention
various methods, methodologies, implements and embodiments may be
employed for measuring the optical properties of teeth and other
materials. While much of the description herein describes exemplary
embodiments employing a probe with a central element serving as a
light source, as will apparent to those skilled in the art
principles, techniques and implements in accordance with the
present invention may be employed in other probe configurations.
The following description discusses additional exemplary
embodiments, methods and systems for distinguishing the optical
properties of teeth and other materials and objects based on such
previous principles, techniques and implements and enhancements
thereof.
[0329] Previously described exemplary embodiments preferably have
utilized probes and methods with one or more source elements,
preferably fiber optics, and one or more receiver elements, also
preferably fiber optics, in order to adjust spectral or other
optical characteristics data for height and angular changes
resulting, for example, from not holding the probe perpendicular to
a surface or to irregularities in a surface. In accordance with
other aspects and exemplary embodiments of the present invention, a
central receiver element, also preferably a fiber optic, will now
be described in more detail.
[0330] Referring now to FIG. 52, an embodiment of the present
invention utilizing probe 800 (illustrated in cross section)
including central receiver 802 (preferably a fiber optic)
surrounded by two rings 806 and 810 of light sources (also
preferably fiber optics). Rings 806 and/or 810 in preferred
embodiments are constructed of strands and/or a ring of fiber
optics. In alternate embodiments rings 806 and 810 are constructed
of cylindrical light guides. FIG. 53 illustrates an embodiment of
the present invention utilizing probe 812 (illustrated in cross
section) including central receiver 814 (also preferably a fiber
optic) surrounded by two rings of sources (preferably fiber optics)
where the inner ring includes a plurality of sources or fiber
optics 816 and 818, preferably six evenly spaced apart, and the
outer ring includes a plurality sources or fiber optics 820,
preferably twelve evenly spaced apart. As will be described in
greater detail later, the use of two rings of light sources in such
embodiments may be in used in accordance with the present invention
to provide a method for measuring the opalescence or other optical
characteristics of materials or objects.
[0331] Consider a probe (such as probe 802 and/or 812) approaching
a material or object. As the probe approaches the surface of the
material or object, the intensity of light reflected from the
material or object and received by a receiver will increase as the
height from the object decreases. Eventually, at a peaking height
the intensity will peak, and as the probe is lowered to the
critical height the intensity will fall to a minimum. This
phenomenon has been described in detail previously herein. In
general, as will be appreciated by those skilled in the art, this
phenomenon does not depend on whether the central element is the
light source and the inner and outer rings are light receivers, or
if the central element is the receiver and the inner and outer
rings are sources. In both cases, the intensity received by a
single or plurality of receiver fibers varies with height.
Similarly, the intensity received by a single or plurality of
receiver fibers varies as the angle of the probe changes from being
normal to the surface. Additionally, if the surface has
irregularities, the intensity also will vary.
[0332] Among the advantages of utilizing a plurality of receiver
fibers is that certain of the receiver fibers can be utilized to
measure angle and height, as previously described. An advantage of
utilizing a single receiver is that the instrument requires only
one light receiver/spectrometer detector. In accordance with other
aspects of the present invention, however, methods and implements
to quantify and/or correct for height and angle with a single
receiver may also be provided.
[0333] Referring again to FIG. 52, in addition to the two rings of
light sources, three monochrome sources 808 (preferably fiber
optics) preferably are positioned in a ring between the two rings
of light sources. FIG. 53 illustrates three monochrome light
sources 816 positioned within the first ring. The number of
monochrome sources and their precise locations are not limited to
what is illustrated, and other arrangements are utilized in other
embodiments for specific applications. It has been determined,
however, that three monochrome sources may be advantageously
utilized in many applications.
[0334] In accordance with such embodiments, monochrome sources 808
and 816 are supplied with monochromatic or nearly monochromatic
light that preferably is out of the band of interest. For color
determination, the optical band of interest is typically 400 to 700
nanometers. Most spectrometers, however, such as those described
elsewhere herein and/or CCD spectrometers such as those
manufactured by Ocean Optics, are sensitive well into the infra-red
light band. Thus, many spectrometers are capable of detecting light
from 700 nanometers to 800 nanometers or even longer
wavelengths.
[0335] In preferred embodiments utilizing this aspect of the
present invention, the three monochromatic light source fibers are
each supplied with monochromatic light of different wavelengths.
One preferred way to provide such monochromatic light is by
utilizing three infra-red LEDs of different wavelengths, for
example, or by filtering a white light source with interference
notch filters with different center wavelengths.
[0336] In one such preferred embodiment, a broad band white light
source supplies light to all light source fibers/light guides.
Light supplied to the three monochromatic light sources is filtered
with narrow band pass notch filters with center wavelengths greater
than 700 nanometers. For example, one center wavelength may be 750
nanometers, while another center wavelength may be 775 nanometers,
and a third center wavelength may be 800 nanometers. It should be
noted that the exact filter wavelengths are not important; it is
only important that such wavelengths be sufficiently different so
that they do not overlap and may be separately detected, as
described herein. The other two rings of light sources include, for
example, a broad-band visible range filter that passes light from
400 to 700 nanometers and rejects light in the range of the three
monochrome filters. What is important is the broad-band light
sources preferably do not emit light in the frequency range of the
monochromatic light sources, or at least do not emit light in such
frequency range to a degree that would interfere with the detection
of the monochromatic light as described herein.
[0337] As such a probe in accordance with the present invention
approaches a material or object, receiver fiber 802 or 814 will
receive visible light and infra-red light as illustrated in FIG.
54. The visible light preferably is spectrally analyzed to
determine the optical properties of the material or object,
preferably as described elsewhere herein. The analyzed spectrum
also will include light intensities at the three monochrome source
center wavelengths as illustrated in FIG. 54 (illustrated as
frequency band 824). The three intensities are independent of each
other and can be utilized to determine height and angle in a manner
similar to that for the perimeter receivers as previously
described.
[0338] Such a probe in accordance with the present invention
preferably is normalized to a standard material. If the probe is
perpendicular to a material, the three out of band intensities
should be equal. If the probe is not perpendicular to the material
they will differ such as is illustrated in FIG. 54. The difference
in the intensities is a function of the angle of the probe with
respect to the surface of the material or object and may be used to
measure and quantify the angular change and to adjust the intensity
of the visible region of the spectrum if desired, as described
elsewhere herein. The intensity of the three out of band
intensities of the monochromatic sources also may be utilized to
determine or quantify the height of the probe as described
elsewhere herein. The three intensities will demonstrate a peaking
phenomena as described earlier. It also should be noted that the
visible band also will demonstrate a peaking phenomena and is
utilized in certain applications/embodiments to determine/quantify
height as well.
[0339] In one alternate embodiment, the three monochrome sources
are not filtered and are supplied light with the same spectral
properties as the inner and outer rings (the three sources in such
embodiments may not be monochrome, but may be broad-band). With
such an alternate embodiment, the light sources may be alternately
turned on and off in a manner synchronous with the measurement of
spectral data. As an exemplary operation of such an alternative, as
the probe approaches a material or object, the inner ring source
may be turned on and a measurement is made. The inner ring may then
be turned off and the outer ring turned on and a measurement is
made. Both inner and outer rings may then be turned off and the
three monochrome (or broadband) sources are each in turn turned on
and off as a measurement is made. The plurality of spectrums or
measurements are utilized to determine the optical properties of
the material and to measure and/or adjust for height and angular
changes in accordance with previously described principles.
[0340] As will be understood from the previous discussion, the use
of at least inner and outer rings of light sources is to provide a
method to determine optical characteristics such as the opalescence
or translucency of the material or object. Such inner/outer rings
may be utilized in conjunction with the three monochrome or other
light sources utilized to determine angle and height as described
earlier. As will be understood from previous description, when the
inner ring of light sources is on it provides light to the material
that is geometrically within a certain angular range. When the
outer ring is on it provides light that is geometrically at larger
angles. If the material is opalescent, for example, a spectral
shift will occur between the two measurements, thereby allowing
such optical characteristics to be quantified.
[0341] Certain spectrometer systems can collect data at high data
rates such as certain spectrometers manufactured by Ocean Optics,
Inc., which can have an integration time of 1 millisecond. In
typical data gathering applications, the spectrometer is run at a
high rate and the data is signal averaged over many samples to
reduce noise. Such signal averaging techniques are well known to
those skilled in the art. In an alternate embodiment of the present
invention, the three monochrome sources each have the same out of
band wavelength. The inner and outer ring sources provide light
filtered or otherwise generated to include only the visible band.
The light provided to the inner and outer rings is gated on and off
as discussed above or one or the other rings is left on (but still
a plurality of spectral measurements preferably are taken). The
three monochrome sources, however, are turned on and off rapidly,
synchronous with the spectral measurements being taken at, for
example, a rate of 1000 Hz. The visible band of the spectrum
preferably are signal averaged to reduce noise and the out of band
sensors preferably are utilized for angle and height
determinations.
[0342] In another alternate embodiment of the invention, the
monochrome light sources and sensors are in band. The light
provided to the inner and outer ring sources are notched to exclude
a small portion of light at the wavelengths of the monochrome
receivers, such as is illustrated in FIG. 55 (see frequency band
826). With such embodiments, the monochrome receivers/sensors may
be of different wavelengths as described earlier or may be of the
same wavelength and pulsed on and off as described earlier.
[0343] It should be noted that such aspects of the present
invention may be applied to embodiments with one or more light
sources and/or with one or more light receivers. The positions of
the sources and sensors illustrated in the figures is for
illustration and discussion purposes only. Such aspects of the
present invention may be applied to any positioning of the source
and receivers consistent with the principles described herein.
Although the present invention was disclosed for light, such
techniques may be applied to other measurement techniques as well,
such as acoustical imaging systems. With such embodiments, height
and/or angle determination, quantification and/or correction may be
applied to a variety of probe configurations, including a probe
with a central element, and including probes in which the central
element is a source or a receiver, etc.
[0344] Yet other aspects of the present invention will now be
described.
[0345] As previously described, certain embodiments of the present
invention may be implemented through the use of a flexible cable
assembly consisting of one or more fiber optics. As previously
described, fiber optics conduct light that is within a certain
angular range or acceptance range of the fiber optic. The range of
angles is quantified by designating a Numerical Aperture (NA) for a
fiber optic, as described elsewhere herein. It has been determined
that the amplitude of light propagating within a fiber optic, and
the spectral properties of the light propagating within a fiber
optic, changes as the fiber optic is bent over small radii. The
degree of amplitude change, spectral shift and angular shift in
general depends upon the geometric properties of the fiber and the
degree of flexing of the fiber. The above spectral, angular and
amplitude shifting can affect spectroscopy measurements and optical
properties measurements in systems that utilize fiber optic
cables.
[0346] One solution to such problems is to provide a cable that is
held rigid or fixed to avoid flexing, such as the "hand held"
embodiments of the present invention described elsewhere herein,
where flexing of the fiber optics is inhibited or prevented.
Another solution is to provide a semi-rigid cable that can not be
flexed over small radii. In some applications such as dentistry,
however, a semi-rigid cable may be undesirable or impractical.
Thus, in accordance with other aspects of the present invention,
techniques are provided to measure or quantify the spectral,
intensity and/or angular shift in such a cable and to utilize such
a measurement to desirably affect the overall optical properties
measurement.
[0347] FIG. 56 illustrates an embodiment of the present invention
utilizing such techniques. Such an embodiment preferably includes a
spectrometer, light sensors, a CPU or computer, a fiber optic cable
and a probe, such as in one or more embodiments described elsewhere
herein. Cable 860 is such a preferred embodiment and contains one
or more source fiber optics (see source fiber optic 838) that
provide light from the light source (a preferred arrangement is
illustrated as lamp 830, hot mirror 832, glass rod 834 and iris
836, such as previously described) to the material or object being
measured and one or more receiver fiber optics that receive light
reflected or returned from the material or object and serve to
provide light to the spectrometer and/or light sensors. Various
embodiments of such a spectrometer and/or light sensors have been
described elsewhere herein. In addition, details of exemplary cable
constructions and methods also have been described elsewhere
herein.
[0348] A cable in accordance with such preferred embodiments
includes one or more additional fibers. Included is at least one
additional source fiber, hereinafter referred to as the secondary
source fiber or cable/lamp drift source fiber (see fiber 840), and
one or more additional receiver fiber(s), hereinafter referred to
as secondary receiver fibers or cable/lamp drift sensor fibers (see
fibers 848, 850, 854 and 855). Such secondary source fiber and
secondary receiver fibers pass down the length of cable 860
parallel to the other fibers (see fibers 838, 846 and 844) in the
cable, and the secondary fibers are joined at probe end 862 in
portion 864 that includes diffusing cavity 866, preferably a small
diffusing cavity such as previously describe herein. Diffusing
cavity 866 serves to cause light provided by secondary source fiber
840 to be presented to secondary receiver fibers 848. Secondary
receiver fibers 848 provide a light path from diffusing cavity 866
to one or more secondary light sensors (see, e.g., sensors 852 and
858). Fibers 844 and/or 846 preferably pass to optical sensors for
purposes of taking spectral or perimeter measurements, as described
elsewhere herein.
[0349] Preferably, one of the secondary light sensors is a
spectrometer for measuring the spectrum of the light source (or
some portion of the spectrum of the light source) after it passes
over the length of the cable and back through the cable (see, e.g.,
filters 856 and sensors 858, implementing one type of spectrometer,
such as previously described elsewhere herein). Another of the
light sensors preferably is a "wide band" sensor pair which
consists of two or more sensors 852 that are positioned to measure
the radial distribution of light in a secondary receiver fiber
optic. The details of such a spectrometer for measuring the
spectrum of the light source and for adjusting the spectral or
other optical characteristics data of such a system in accordance
with embodiments of the present invention have been described
elsewhere herein. The details of such a "wide band" sensor that
measures the angular distribution of light within a fiber optic
have also been described elsewhere herein.
[0350] In accordance with such embodiments, the spectrum of the
secondary receiver fibers is measured and saved as part of a
normalization process (e.g., with the cable in an unflexed or known
flexed condition, etc.; e.g., a first degree of flex). The
intensity and angular distribution pattern of the secondary
receiver fiber(s) similarly are measured and saved as part of the
normalization process. As the system is utilized following the
normalization process, the spectrum and angular distribution of the
lamp and secondary receiver fibers are monitored while other system
measurements (e.g., spectral measurements as described previously)
are being taken. In general, if the secondary spectrum and angular
distribution do not change, the cable has not been flexed. If,
however, there is a change in such parameters, either the lamp
spectral properties (including angular distribution such as caused
by heating of lamp elements or apertures or infrared filters, etc.)
has changed, or the cable has been flexed (e.g., to a second degree
of flex, different from the first degree of flex) or otherwise
changed to a degree to produce a detectable change. Such changes
may thus be measured and monitored.
[0351] By providing additional sensors to monitor the lamp source
directly such as described herein, it can be determined if the
cable is being flexed or if the lamp and/or lamp hardware are
changing. In certain applications it may not be necessary to
determine which is changing (e.g., either cable flexing or lamp
drift), but to simply monitor the overall system drift/changes and
adjust the measurements to compensate for drift or to reject the
measurements if the system has drifted out of calibration. Such use
of normalization data and monitoring of the lamp and cable, etc.,
is used in preferred embodiments to compensate, and accept or
reject, spectral or other optical characteristics data taken in
accordance with the present invention.
[0352] It should be noted that such embodiments may be used, for
example, as a strain gauge or as an instrument to measure if the
curvature in a system is changing (see Apparatus and Method for
Detecting Curvature filed on even date herewith by the inventors
hereof, which is hereby incorporated by reference). In addition,
such embodiments may be applied to one or more secondary source
fibers and one or more secondary receiver fibers. Such embodiments
also may utilize a plurality of secondary source and receiver
fibers and a plurality of diffusing cavities distributed along the
length of a cable assembly to quantify not only whether or not a
cable is being flexed (and to measure and quantify the degree of
flexing), but at what point or approximately what point in the
cable the flex is occurring.
[0353] The secondary source fiber optic also may be provided by the
primary source fiber optic utilizing mirrors or the like, or by
notching the source fiber and providing a small amount of light to
the secondary receiver fibers. What is important in such
embodiments is that a portion of the light from the primary source
fiber be controllably provided to the secondary receiver fiber(s).
Additionally, in a system with a plurality of secondary receiver
fibers, one secondary (or primary) source fiber may be utilized to
provide sufficient light to all secondary receiver fibers in order
for flex determination/quantification purposes in accordance with
the present invention. The secondary source fiber may alternately
have a light source different from the primary source fiber, and
separate correction factors may be accordingly determined for the
lamp and for the cable flexing.
[0354] It also should be noted that the diffusing cavity optionally
may be replaced by a single fiber that serves both as a secondary
source and secondary receiver fiber by looping the fiber optic back
in the probe (or creating an equivalent of a fiber or optic loop).
In accordance with such optional embodiments, two strands of fibers
run the length of the cable and serve as a secondary source fiber
and a secondary receiver fiber.
[0355] In an alternate embodiment, no additional fibers are added
to the probe but a mirror such as a hot mirror is mounted or
positioned near the end of the probe permitting light of certain
frequencies, preferably frequencies that are out of the visible
band, to be reflected/returned from one or more primary source
fibers to one or more primary receiver fibers. The out of band
light frequencies preferably are detected by sensors with notch
filters that reject in band light frequencies as discussed earlier
herein and that are primarily sensitive to flexing of the
cable.
[0356] Again, what is important is that a secondary receiver fiber
(or equivalent return optical path) couple light to optical sensors
so that spectral or other changes due to cable flexing and/or lamp
drift or the like may be determined and/or quantified, with such
flex and/or lamp drift-type data available for correction or
further quantification of optical characteristics data in
accordance with the present invention.
[0357] Still other aspects of the present invention will now be
described.
[0358] FIG. 57 illustrates one or more systems 870A, 870B . . .
870N having probes 874A, 874B . . . 874N, preferably constructed
and operated in accordance with previously described embodiments,
each of which is adapted to include a modem (illustrated as modems
872A, 872B . . . 872N). The modems may be a part of, or coupled to,
the CPU, computer or other processing unit included as part of
systems 870A, 870B . . . 870N (the use of CPUs, computers or other
processing units as part of such systems is described elsewhere
herein).
[0359] In accordance with such embodiments, under user initiated or
other software control (such as a periodic call-in determined by
software timing/real time clock algorithm, boot-up algorithm,
etc.), one or more of systems 870A, 870B . . . 870N is coupled
effectively to lab 884. Illustrated in FIG. 57 is an illustrated
embodiment in which systems 870A, 870B . . . 870N are coupled via
modem connection to web page 878, which for illustrative purposes
is maintained on internet service provider (ISP) node 876. Lab 884
may include node 876, or lab 884 may be coupled to node 876 through
a dedicated, dial-in or other connection. What is important is that
systems 870A, 870B . . . 870N are able to coupled to a central
electronic point that is a part of, or accessible by, lab 884. Lab
884 in this embodiment serves as a location for purposes of
monitoring, controlling, servicing, etc., one or more of systems
870A, 870B . . . 870N, as will described. In a typical application,
lab 884 may be a part of, or working in conjunction with, the
entity that manufactures, maintain, services or operates systems
870A, 870B . . . 870N, etc., or uses such systems as part of an
industrial process, examples of which are described elsewhere
herein.
[0360] It should also be noted that the use of a web page and
internet connection is illustrative only. As illustrated by
connection 882, the connection between lab 884 and one or more of
systems 870A, 870B . . . 870N may be made directly between the
system(s) and lab 884, such as by modem or other electronic
connection, either direct or over some wide area or other
network.
[0361] In accordance with such embodiments, systems 870A, 870B . .
. 870N may be electronically coupled to lab 884, which preferably
is remotely located from one or more of the various systems. In one
embodiment, lab 884 is able to convey operational commands to one
or more of the systems. In one aspect of the present invention, one
or more of systems 870A, 870B . . . 870N receive commands
initiating a diagnostic or test mode, in response to which the
system executes a diagnostic routine that generates diagnostic data
(indicative of the operational status, failure mode or other
diagnostic type data), which may be coupled to lab 884 by the
electronic connection. In other aspects, during normal operation,
one or more of the systems periodically capture and store
operational data, such as lamp characteristics, calibration or
normalization data or the like. The periodic storing of such
operational data may be software initiated and/or controlled based
on time (e.g., number of lamp or system operating hours),
measurements, boot-up or initialization or other triggering event.
Upon periodic or other connection to lab 884, such operational data
may be transferred to lab 884 for evaluation, analysis, statistical
processing and/or storage. In one such embodiment, lab 884 stores a
history of such operational data for statistical or diagnostic
purposes, such as for initiating a service call for the system,
advising or predicting a need for a future service call (such as
lamp, filter or other component replacement or repair). As an
exemplary application, lab 884 monitors such operational data for
key components (such as a light source) over time, and using stored
data, look-up table or algorithm predicts remaining life of the
component. Thereafter, lab 884 may send data or commands to one or
more of systems 870A, 870B . . . 870N in order to have a suitable
diagnostic, service call, informational or other message displayed
on the system and/or a computer coupled to the system. In still
other refinements of such embodiments, lab 884 may also generate an
internet or other electronic message to a person or entity
providing a status report or other data with respect to the
particular system being monitored, diagnosed, controlled, etc.
[0362] In accordance with such embodiments, lab 884 may also use
such an electronic connection to download software upgrades or
other modifications to one or more of systems 870A, 870B . . .
870N. As exemplary uses, such software upgrades may consist of bug
fixes or new releases of application, operating system, shade guide
data or other software. In accordance with other aspects of the
present invention, normalization or other data files (such as
normalization, calibration or other files determined by the
particular application, or files containing parameters controlling
or used in a signal processing or filtering algorithm or the like)
may be utilized by the system to make measurements or control
decisions (for example, in one of the industrial applications
described earlier), with such data files being upgradeable or
reconfigurable by under software control, which may be done
remotely with a remote electronic connection as described
earlier.
[0363] As a particular example, one or more of the systems may
output shade guide values, such as for a dental application. In the
event that new or updated shade guides are released, new or updated
shade guide values may be electronically transferred to the one or
more systems, thereby reducing downtime of the instrument, physical
service calls or the like. Similar, in certain industrial
applications, files indicative of or corresponding to particular
materials or objects being optically characterized may be
electronically downloading to one or more such systems (e.g., files
that assist such a system in characterizing, identifying or sorting
materials or objects that are being processed in a industrial,
manufacturing or inventorying process, etc.). In applications in
which constituent materials of a material or object are being
predicted (either the material or object being optically
characterized or a second material or object to be produced based
on the material being optically characterized), files indicative of
or corresponding to such constituent materials may be
electronically downloading (also including recipe formulas and the
like).
[0364] In accordance with another such aspect of the present
invention, two or more systems may be coupled to lab 884, either in
a simultaneous (parallel) or sequential (serial) manner in order to
have either the same or different data files, software or other
information to the two or more systems, such as for facilitating
operation of the two or more systems that is synchronized in some
manner (such as downloading calibration, normalization or other
data files that enable or facilitate a more synchronized or
corresponding operation between or among the two or more
units).
[0365] It should also be noted that systems in accordance with the
present invention may internally store operational data or other
information such as for key components (e.g., light source) and
predicting failure or a need for replacement or servicing of the
component, with an appropriate message or alarm provided to a user.
Monitoring the operating characteristics or duration of operation,
etc. for key components may thus be implemented without being
coupled to a remote lab.
[0366] Aspects of the present invention relating to calibration of
systems in accordance with the present invention will now be
described with reference to FIG. 58.
[0367] In certain applications, it may be desirable to calibrate
system 888, which may optionally include modem 898 or other
communication device, by directing probe 890 towards color or other
standard 892. Measurements taken as probe 890 is directed towards,
or in proximity to, standard 892 may then be captured and stored
and used to normalize, calibrate or otherwise adjust spectral
measurements taken by the system. In accordance with certain
preferred embodiments, such a calibration step is performed prior
to measuring each object or material, or series of objects or
materials.
[0368] It also is contemplated by the present invention that as
probe 890 is in the process of being moved relative to standard 892
sensors 894 detect the position of probe 890 with respect to
standard 892 or a common physical reference point. Using sensors
894, a series of calibration or normalization measurements may be
taken at determined positions relative to standard 892, with such
positional information available for normalization or other
adjustment of spectral or other measurements taken by the
instrument.
[0369] Arrow 896 denotes that the motion of probe 890 with respect
to standard 892 is a relative motion, and either the probe or the
standard may be moved with respect to the other. In certain
embodiments, probe 890 is retained in a fixed position, and
standard 892 is moved towards probe 890 in a controlled manner,
while sensors 894 similarly detect and provide information
indicative of the relative position of the probe with respect to
the standard. Standard 892 may be controllably moved by a servo
motor or the like in order to provide the desired, controlled
relative movement between the probe and the standard. If system 888
includes modem 898 or the like, a remote lab or operator may
initiate, control, monitor and/or receive data from the calibration
or normalization process in a manner similar to that described in
connection with FIG. 57.
[0370] In conjunction with various of the foregoing embodiments, a
variety of optic fibers may be utilized, with smaller fibers being
used to assess optical characteristics of smaller spots on the
object or material under evaluation. In accordance with such
aspects of the present invention and with various of the
embodiments described herein, fibers of about 300 microns in
diameter, and up to or less than about 1 millimeter in diameter,
and from about 1 to 1.5 millimeters have been utilized, although
fibers of other diameters also are utilized in other embodiments
and applications of the present invention. With such fibers, the
optical properties of the object or materials under evaluation may
be determined with a spot size of about 300 microns, or
alternatively about 1 millimeter, or about 1.5 millimeters, or from
about 0.3 to 1 millimeters, or from about 1 to 1.5 millimeters. In
accordance with such embodiments, optical properties of such a spot
size, including spectral, translucence, opalescence, gloss, surface
texture, fluorescence, Rayleigh scattering, etc., may be quantified
or determined, including by determining a plurality of spectrums as
the probe is directed towards or in contact or near contact with
the object or material and possible changes in such spectrums, all
with an instrument that is simply directed towards a single surface
of the object or material under evaluation.
[0371] It also should be noted that, in accordance with various
principles of the various embodiments of the present invention
described herein, refinements may be made within the scope of the
present invention. Variations of source/receiver combinations may
be utilized in accordance with certain embodiments of the present
invention, and various optical properties may be determined in
accordance with the various spectra obtained with the present
invention, which may include spectra taken at one or more distances
from the object or material (and including spectrally reflected
light), and spectra taken at or near the surface (e.g., within the
critical height, and substantially or wholly excluding spectrally
reflected light). In certain embodiments, measurements may be taken
in a manner to produce what is sometimes considered a goniometric
measurement or assessment of the object or material under
evaluation. In other embodiments, features may sometimes be used
with or without certain features. For example, certain applications
of aspects of the present invention may utilize perimeter fibers
for height/angle determination or correction, while other
applications may not. Such refinements, alternatives and specific
examples are within the scope of the various embodiments of the
present invention.
[0372] Various other features, embodiments, alternatives, etc., in
accordance with the present invention will now be described.
[0373] As previously described, various devices, systems, methods,
and methodologies for measuring the optical properties of teeth and
other materials may be obtained in accordance with the present
invention. Various embodiments herein utilize a spectrometer and
other optical sensors. Particular preferred embodiments previously
described preferably utilize light-to-frequency converters such as
the TSL230 sensor manufactured by Texas Instruments. Such
embodiments include many unique and/or advantageous properties. As
will be understood based on the disclosures herein, one such
property is that the precision of the measurements for each
spectral band may be independent of light intensity within the
band. As a result, for example, the more blue bands, which
typically have the lowest light intensity, may be measured with the
same precision as the more red bands, which typically have the
highest light intensity (please see the prior description of
embodiments utilizing the TSL-type sensors).
[0374] Alternative embodiments may utilize linear or matrix charge
coupled device (CCD) technology or other linear and/or matrix
optical sensors as a spectrometer system (exemplary alternative
embodiments are described elsewhere herein). It has been
determined, however, that utilizing CCD or other linear or matrix
sensors may present certain problems and disadvantages. One such
difficulty is that the light sensitivity of light in the more blue
bands is considerably less than the light sensitivity or intensity
of light in the more red bands. The reduced sensitivity is due to
the nature of the sensing elements and also due to the spectral
properties of the light source and the spectral properties of the
light conduction elements. It is not unusual in spectrometer
systems, particularly in reflectance-type systems, for the blue
system sensitivity to be several orders of magnitude less than the
red sensitivity. Thus, if the spectrometer system is constructed
with a linear or matrix array where the light receivers intensity
is output serially to an analog to digital converter (ADC), then
the range of the ADC and the precision of the ADC must be large
enough to accommodate the high red light sensitivity (or else the
system will saturate rendering the measurement invalid) and it must
also be precise enough to permit the low sensitivity elements to
have sufficient gain to make quality measurements. For example, if
the red intensity and sensitivity is 128 times the blue intensity
and sensitivity, then in general the blue readings will
automatically have a precision that is 128 (2.sup.7) times less
than that for red. If, for example, a 16 bit ADC is utilized and
providing 2.sup.16 levels of gray, then the maximum level of gray
for blue is 128 times less or (2.sup.(16-7)) or only 2.sup.9 levels
of gray. In general, if a 10 bit ADC is utilized, blue will only
have eight levels of gray, etc.
[0375] One approach in certain spectrometer systems, particularly
those utilized for reflectance measurements, has been to optically
normalize in order to flatten the spectral response. This may be
done, for example, by reducing the intensity of the red light input
to the spectrometer with filters or mirrors or the like, such as
interference filters, to reduce the intensity of red light on the
sensors and force the red intensity to be within the range of the
blue sensors. The disadvantage of such systems is that it causes
the noise level of the red sensors to be increased to the noise
level of the blue sensors since the signal from the red sensors is
reduced, requiring an increase in overall system gain, hence the
system noise is forced to the level of the lowest sensitivity
input.
[0376] In accordance with other alternative embodiments of the
present invention, improved spectrometer-type systems may be
produced. FIG. 59 is a block diagram of one such alternative
embodiment. As illustrated, linear (or array) optical sensor 900,
which preferably includes an optical manifold that receives and
directs light of a given wavelength to appropriate sensing elements
provided in linear optical sensor 900. Optical manifolds that
direct light of a given wavelength are known in the art and may be
constructed, for example, of diffraction gratings or optical
filters (such as the optical manifolds and implements of the type
described elsewhere herein). The output of linear optical sensor
900 passes through variable gain amplifier 906, to sample and hold
amplifier 908 and to analog-to-digital converter (ADC) 910. Such
variable gain amplifiers, sample and hold amplifiers and ADCs are
known in the art and are sometimes available as a single unit. It
is desired that the ADC have the desired precision and that the
overall system provide for the speed required for the particular
application.
[0377] In the illustrated embodiment, system timing is controlled
by timing generator 902, coupled to computer 904 (which also
preferably receives data from ADC 910). Timing generator 902
optimally controls linear optical sensor 900 (or CCD or other
linear sensor, etc.) to integrate a measurement and to output it to
variable gain amplifier 906 and sample and hold amplifier 908 and
ADC 910. Timing generator 902 also preferably controls the analog
output of linear optical sensor 900 to serially step from one
sensor to the next in a controlled and desired manner.
[0378] In accordance with such embodiments, variable gain amplifier
906 is also controlled by timing generator 902 and/or computer 904,
and preferably the gain of variable gain amplifier 906 is varied
step by step and, preferably, uniquely for each sensor in the liner
optical sensor 900. Thus, in accordance with such embodiments, the
gain corresponding to a given first (e.g., red) element may be
different than the gain for a given second (e.g., blue or green)
element under control of timing generator 902 and/or computer 904.
In accordance with such embodiments, the full (or substantially all
of the) range of ADC 910 thus becomes available for each sensor,
and timing generator 902 and/or computer 904 can normalize or cause
the overall system sensitivity to be flat over the entire spectral
range.
[0379] In certain embodiments, timing generator 902 is controlled
by a computer or microprocessor or is a microprocessor such as a
RISC processor such as a Hitachi SH2 or SH3 processor. In such
embodiments the gain of variable gain amplifier 906 is variable
dynamically by the processor as spectral measurements are being
made. It also should be noted that such embodiments preferably
utilize a linear-type array sensor, although such embodiments also
may utilize matrix-type sensor elements or individual elements as
well. What is important is that the sensing elements be provided
with suitable gain for the light intensity presented to the
particular sensing elements, etc.
[0380] Yet other alternative embodiments in accordance with the
present invention will now be described.
[0381] As described previously, embodiments in accordance with the
present invention typically utilize a spectrometer and/or other
optical sensors. The measurements preferably were made while the
probe was in motion with respect to the material being
measured--either the probe was moving, the material was moving, or
both. In accordance with such embodiments, it is desired that both
rapid and precise measurements be made over the entire spectral
range.
[0382] Making rapid spectral measurements with precision typically
has been difficult or impossible to do because a spectrometer that
can make rapid measurements typically consists of a plurality of
light sensors, each measuring a small spectral region or band
simultaneously in a parallel fashion, as opposed to an apparatus
consisting of one optical sensor that measures spectral bands in
sequence or serially one after the other. In general, an instrument
that measures spectral bands in a parallel fashion can produce N
times as many measurements per unit time as an instrument making
serial measurements, assuming that the spectral receivers in both
instruments are equivalent. In either case, whether the apparatus
has many simultaneous sensors or one sensor making multiple
measurements, in general the more rapid the apparatus operates, the
shorter the integration time per spectral band, and hence the lower
the precision of the spectral measurement.
[0383] In accordance with other alternative embodiments of the
present invention, the precision and/or sampling rate of such
spectrometers may be increased.
[0384] As described elsewhere herein, in accordance with preferred
embodiments the spectral properties of materials may be measured as
a probe moves into contact with or into proximity with an object.
When the probe is far from the object, the total light energy
received is small, and as it is moved towards the object the
optical energy increases and eventually peaks and decreases as the
probe is moved still further towards the material. In alternative
probe designs, the light energy may not peak but may rise to a
maximum as the prove is moved into contact or near contact with the
material. In either case, peaking or not, as the probe moves
relative to the material the total spectral energy received will
vary.
[0385] Certain materials exhibit properties such as opalescence or
pearlesence wherein the spectral reflectance curve is a function of
angle of incidence and angle of reflection. Other materials
(perhaps most materials) have consistent spectral reflectance
curves that are not functions of angle (at least for angles within
a limited range of angles). What does vary, however, for virtually
all materials is the value or gain of the spectrum as a probe moves
relative to an object. When the probe is far away the value will be
low, and as it nears the object the value will increase. In many
cases the value or gain will vary by orders of magnitude while the
spectral shape or chroma will vary relatively little.
[0386] In accordance with alternative embodiments, it has been
determined to be advantageous to measure the value of a spectrum
for a probe moving relative to a material at a high rate (or at a
first rate high enough to "freeze" the value at a precise location
or range of locations), while it is only be necessary to measure
the chroma at a second, lesser, rate and hence with higher
precision.
[0387] FIG. 60 illustrates a preferred exemplary implementation of
such an embodiment of the present invention. Such an embodiment
preferably includes a reflectance-type probe having at least one
light source and at least one light receiver element (examples of
such probes and light sources/receivers are described elsewhere
herein; FIG. 60 illustrates for discussion purposes only light
receiver 912). Light receiver 912 couples received light to optical
splitter 914, which couples received light to spectrometer 916 and
also to wide band (value) sensor 918. In accordance with such
embodiments, spectrometer 916 (which may be of a design/type
described elsewhere herein) preferably measures the spectral
properties of the received light as a function of optical
wavelength over a band range such as the visible band (400 nm to
700 nm). Wide band sensor 918 preferably measures the light energy
over a wide band, and preferably over the same total band as
spectrometer 916.
[0388] Without being bound by theory, if V is the measurement of
value/wide band sensor 918, and R(.lamda.) is the reflectance
response of the material as a function of wavelength, then for
static measurements or measurements where V and R(.lamda.) are made
at the same rate:
v = .intg. band R ( .lamda. ) .lamda. = bands R ( .lamda. )
##EQU00008##
[0389] Value/wide band sensor 918 in general will always have an
intensity much higher than the intensity of any of the individual
spectral sensors of spectrometer 916 since it measures the light
intensity over a broad band of wavelengths. Hence if the chroma of
the spectrum varies slowly (such as a function of angle), it is
possible to measure the spectrum at a rate much less than the rate
of the Value sensor, thus improving the precision of the spectral
sensors. Preferably, however the value of the spectral sensors is
adjusted to account for the variation in value due to the movement
of the probe/material, or the reflectance spectrum should be
adjusted by a gain factor G where:
G = V bands R ( .lamda. ) ##EQU00009##
and hence the adjusted reflectance spectrum with improved precision
is:
R.sub.a(.lamda.)=GR(.lamda.)
[0390] As will be appreciated, in accordance with such alternative
embodiments sensors and means are provided to measure value at a
first, preferably faster rate, and chroma at a second, preferably
slower rate, in such a manner to make more precise and overall
rapid measurements.
[0391] Still other alternative embodiments of the present invention
will now be described.
[0392] As previously described, various devices, systems, methods,
and methodologies for measuring the optical properties of teeth and
other materials may be obtained in accordance with the present
invention. In preferred embodiments, an instrument with a
spectrometer and with "wide band" optical sensors is utilized. In
general, the spectrometer measures optical intensities over narrow
optical bandwidths, while the wide band sensors measured optical
intensities over wide band width, typically over the entire visible
spectrum.
[0393] An alternative embodiment in accordance with the present
invention will now be described. As illustrated in FIG. 61, optical
sensor 920 consisting of a spectrometer (narrow band sensors) and
wide band optical sensors are provided. Optical sensor 920
preferably consists of CCD (charge coupled device) 926 (or similar
optical sensing device) for measuring light intensities, and CCD
timing, control and digitizing electronics 928 for converting the
analog output of CCD 926 into digital form (such as may be input
into a computer or microprocessor or other data recording or
analyzing device as described elsewhere herein). CCDs and the
electronics for controlling and digitizing their output are known
in the art.
[0394] In accordance with the illustrated embodiment, the optical
elements of CCD 926 preferably are covered by optical filters 922
and 924, which preferably consists of one or more filter plates.
Such a filter plate preferably is constructed of interference
filters which pass light of a predetermined frequency and reflect
light that is out of band. Interference filters are known in the
art. In the preferred implementation of such embodiments, a portion
(922) of the interference filters pass light with a narrow band
width, while another portion (924) of the filters pass light with
wide bandwidth. Thus, certain of the sensors in CCD 926 may serve
to detect narrow band width light, while other of the sensors may
serve to detect wide band width light. Thus, the output of CCD 926
preferably may include both the elements of a spectrometer and also
the elements of a plurality of wide band sensors (which may be
advantageously utilized as described elsewhere herein).
[0395] In an alternate such embodiment of the invention, CCD 926
may be coupled to diffraction grating 932 as illustrated in FIG.
62. Diffraction gratings such as diffraction grating 932 are known
in the art and have been utilized extensively with CCD-type
sensors. In an embodiments such as illustrated in FIG. 62, however,
diffraction grating 932 covers (or provides diffracted light to)
only a portion of CCD 926, allowing the remainder of the sensing
elements of CCD 926 to be available for a plurality of wide band
sensors (e.g., to receive from wide band filters 924).
[0396] It should be understood that, in accordance with the various
alternative embodiments described herein, various spectrometer-type
devices, and uses and methods based on such devices, may be
obtained. The various refinements and alternative and additional
features also described may be combined to provide additional
advantageous combinations and the like in accordance with the
present invention.
[0397] Reference is made to the following copending applications,
all by the inventors hereof, which are hereby incorporated by
reference: U.S. application Ser. No. 09/091,208, filed on Jun. 8,
1998, which is based on International Application No.
PCT/US97/00126, filed on Jan. 2, 1997, which is a continuation in
part of U.S. application Ser. No. 08/581,851, now U.S. Pat. No.
5,745,229, issued Apr. 28, 1998, for Apparatus and Method for
Measuring Optical Characteristics of an Object; U.S. application
Ser. No. 09/091,170, filed on Jun. 8, 1998, which is based on
International Application No. PCT/US97/00129, filed on Jan. 2,
1997, which is a continuation in part of U.S. application Ser. No.
08/582,054, now U.S. Pat. No. 5,759,030 issued Jun. 2, 1998, for
Apparatus and Method for Measuring Optical Characteristics of
Teeth; PCT Application No. PCT/US98/13764, filed on Jun. 30, 1998,
which is a continuation in part of U.S. application Ser. No.
08/886,223, filed on Jul. 1, 1997, for Apparatus and Method for
Measuring Optical Characteristics of an Object; PCT Application No.
PCT/US98/13765, filed on Jun. 30, 1998, which is a continuation in
part of U.S. application Ser. No. 08/886,564, filed on Jun. 30,
1998, for Apparatus and Method for Measuring Optical
Characteristics of Teeth; U.S. application Ser. No. 08/886,566,
filed on Jul. 1, 1997, for Method and Apparatus for Detecting and
Preventing Counterfeiting; and U.S. application Ser. No.
09/113,033, filed Jul. 9, 1998, for Method and Apparatus for
Measuring Optical Properties of an Object.
[0398] Additionally, it should be noted that the implements and
methodologies may be applied to a wide variety of objects and
materials, illustrative examples of which are described elsewhere
herein and/or in the co-pending applications referenced above.
Still additionally, embodiments and aspects of the present
invention may be applied to characterizing gems or precious stones,
minerals or other objects such as diamonds, pearls, rubies,
sapphires, emeralds, opals, amethyst, corals, and other precious
materials. Such gems may be characterized by optical properties (as
described elsewhere herein) relating to the surface and/or
subsurface characteristics of the object or material. As
illustrative examples, such gems may be characterized as part of a
buy, sell or other transaction involving the gem, or as part of a
valuation assessment for such a transaction or for insurance
purposes or the like, and such gems may be measured on subsequent
occasions to indicate whether gem has surface contamination or has
changed in some respect or if the gem is the same as a previously
measured gem, etc. Measuring a gem or other object or material in
accordance with the present invention may be used to provide a
unique "fingerprint" or set of characteristics or identification
for the gem, object or material, thereby enabling subsequent
measurements to identify, or confirm the identity or non-identity
of, a subsequently measured gem, object or material.
[0399] It also should be noted that the implements and
methodologies described in the co-pending applications referenced
above also may be applied to embodiments and features of the
present invention as described herein. All such refinements,
enhancements and further uses of the present invention are within
the scope of the present invention.
* * * * *