U.S. patent application number 16/284514 was filed with the patent office on 2019-06-20 for near infrared imaging using laser arrays with distributed bragg reflectors.
The applicant listed for this patent is OMNI MEDSCI, INC.. Invention is credited to Mohammed N. ISLAM.
Application Number | 20190183346 16/284514 |
Document ID | / |
Family ID | 51021944 |
Filed Date | 2019-06-20 |
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United States Patent
Application |
20190183346 |
Kind Code |
A1 |
ISLAM; Mohammed N. |
June 20, 2019 |
NEAR INFRARED IMAGING USING LASER ARRAYS WITH DISTRIBUTED BRAGG
REFLECTORS
Abstract
A smart phone or tablet includes laser diodes, at least some of
which may be pulsed and generate near-infrared light and include
Bragg reflectors to direct light to tissue/skin. An array of laser
diodes generates near-infrared light and has an assembly in front
of the array that forms the light into a plurality of spots on the
tissue/skin. A receiver includes detectors that receive light
reflected from the tissue/skin. An infrared camera receives light
reflected from the tissue/skin and generates data based on the
received light. The smart phone or tablet is configured to generate
a two-dimensional or three-dimensional image using at least part of
the data from the infrared camera.
Inventors: |
ISLAM; Mohammed N.; (Ann
Arbor, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
OMNI MEDSCI, INC. |
Ann Arbor |
MI |
US |
|
|
Family ID: |
51021944 |
Appl. No.: |
16/284514 |
Filed: |
February 25, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16016649 |
Jun 24, 2018 |
10213113 |
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16284514 |
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15860065 |
Jan 2, 2018 |
10098546 |
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16016649 |
|
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|
15686198 |
Aug 25, 2017 |
9861286 |
|
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15860065 |
|
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15357136 |
Nov 21, 2016 |
9757040 |
|
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15686198 |
|
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14651367 |
Jun 11, 2015 |
9500635 |
|
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PCT/US2013/075736 |
Dec 17, 2013 |
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15357136 |
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61747477 |
Dec 31, 2012 |
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61754698 |
Jan 21, 2013 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01N 33/15 20130101;
G01J 2003/2826 20130101; A61C 19/04 20130101; G01N 21/3563
20130101; G01N 2021/3595 20130101; G01N 2201/06113 20130101; A61B
5/14532 20130101; H01S 3/06758 20130101; G01N 2021/399 20130101;
G01N 33/49 20130101; A61B 5/7257 20130101; A61B 2562/146 20130101;
G01J 3/453 20130101; A61B 2562/0238 20130101; A61C 1/0046 20130101;
G01M 3/38 20130101; G01J 3/1838 20130101; H01S 3/0092 20130101;
H01S 3/302 20130101; A61B 2562/0233 20130101; G01J 3/108 20130101;
G01J 2003/1208 20130101; G01N 33/02 20130101; G01J 3/2823 20130101;
G16H 40/67 20180101; A61B 5/0086 20130101; A61B 2576/02 20130101;
A61B 5/7203 20130101; G01N 21/359 20130101; G01N 2201/061 20130101;
G01N 2201/062 20130101; A61B 5/1455 20130101; G01N 2201/12
20130101; G01J 3/42 20130101; G01N 33/025 20130101; G01N 2201/08
20130101; A61B 5/0024 20130101; G01N 21/85 20130101; A61B 5/0022
20130101; A61B 5/4547 20130101; A61B 5/0013 20130101; A61B 5/6801
20130101; G01J 3/28 20130101; G01N 21/35 20130101; A61B 5/0088
20130101; G01J 3/0218 20130101; A61B 5/14546 20130101; G01N 33/442
20130101; G06F 19/00 20130101; A61B 5/7405 20130101; G01J 3/14
20130101; G01N 2201/129 20130101; G01J 2003/104 20130101; G01N
21/88 20130101; G01N 21/39 20130101; G01N 21/9508 20130101; A61B
5/742 20130101; A61B 5/0075 20130101 |
International
Class: |
A61B 5/00 20060101
A61B005/00; G16H 40/67 20060101 G16H040/67; G01N 33/15 20060101
G01N033/15; G01J 3/10 20060101 G01J003/10; G01J 3/28 20060101
G01J003/28; G01J 3/42 20060101 G01J003/42; G01J 3/453 20060101
G01J003/453; A61B 5/145 20060101 A61B005/145; A61B 5/1455 20060101
A61B005/1455; G01N 21/35 20060101 G01N021/35; G01N 21/3563 20060101
G01N021/3563; G01N 21/359 20060101 G01N021/359; G01N 21/39 20060101
G01N021/39; G01N 21/88 20060101 G01N021/88; G01N 33/02 20060101
G01N033/02; G01J 3/02 20060101 G01J003/02; A61C 19/04 20060101
A61C019/04; G01J 3/14 20060101 G01J003/14; G01N 33/49 20060101
G01N033/49; G01N 33/44 20060101 G01N033/44 |
Claims
1. A smart phone or tablet, comprising: a first at least one of a
plurality of laser diodes, the first at least one of the plurality
of laser diodes configured to be pulsed; a second at least one of
the plurality of laser diodes; the plurality of laser diodes
configured to generate light having one or more optical
wavelengths, wherein at least a portion of the one or more optical
wavelengths is a near-infrared wavelength between 700 nanometers
and 2500 nanometers, and wherein at least one of the plurality of
laser diodes comprises one or more Bragg reflectors; at least a
portion of light generated by the plurality of laser diodes capable
of being directed to tissue comprising skin; an array of laser
diodes configured to generate light having one or more optical
wavelengths, wherein at least a portion of the one or more optical
wavelengths is a near-infrared wavelength between 700 nanometers
and 2500 nanometers, and wherein at least one laser diode of the
array of laser diodes comprises one or more Bragg reflectors; an
assembly in front of the array of laser diodes configured to
receive at least a portion of the light from the array of laser
diodes, the array of laser diodes and the assembly configured to
form the light into a plurality of spots and configured to direct
at least some of the spots to the tissue; a first receiver
comprising a plurality of detectors, wherein the plurality of
detectors comprises one or more detector arrays; at least one of
the plurality of detectors configured to receive at least a portion
of light from the first at least one of the plurality of laser
diodes and configured to generate a reference detector output, and
at least another of the plurality of detectors configured to
receive at least a portion of light reflected from the tissue from
the first at least one of the plurality of laser diodes and
configured to generate a sample detector output, wherein the first
receiver is configured to generate a first receiver output by
comparing the reference detector output and the sample detector
output; an infrared camera configured to generate data based at
least in part on light received from the second at least one of the
plurality of laser diodes reflected from the tissue; wherein the
smart phone or tablet is configured to receive and process at least
a portion of the first receiver output, and configured to generate
a two-dimensional or three-dimensional image using at least some of
the data from the infrared camera, and wherein the two-dimensional
or three-dimensional image is used in part to identify one or more
features corresponding to the skin; and the smart phone or tablet
further comprising a wireless receiver, a wireless transmitter, a
display, a voice input module, and a speaker.
2. The smart phone or tablet of claim 1, wherein the first receiver
is configured to perform a time-of-flight measurement by measuring
a time difference between the generated light from the first at
least one of the plurality of laser diodes and light reflected from
the tissue from the first at least one of the plurality of laser
diodes, and wherein the smart phone or tablet is configured to
receive and process at least a portion of the time-of-flight
measurement.
3. The smart phone or tablet of claim 1, wherein the infrared
camera is further configured to: generate a first signal in
response to light received while the plurality of laser diodes and
the array of laser diodes are off; and generate a second signal in
response to light received while at least one of the plurality of
laser diodes or at least one laser diode of the array of laser
diodes is on, the light received including at least some light from
the at least one of the plurality of laser diodes reflected from
the tissue or at least some light from the array of laser diodes
reflected from the tissue; wherein the smart phone or tablet is
further configured to use a difference between the first signal and
the second signal to, at least in part, generate the
two-dimensional or three-dimensional image.
4. The smart phone or tablet of claim 1, wherein the first receiver
further comprises one or more filters in front of the one or more
detectors to select a fraction of the one or more optical
wavelengths, wherein at least some of the plurality of laser diodes
operate near a 940 nanometer wavelength, and wherein the smart
phone or tablet is configured to process the two-dimensional or
three-dimensional image using a multivariate analysis.
5. The smart phone or tablet of claim 1, wherein the second at
least one of the plurality of laser diodes is also configured to be
pulsed, and wherein the infrared camera is configured to be
synchronized to the second at least one of the plurality of laser
diodes.
6. The smart phone or tablet of claim 1, wherein the second at
least one of the plurality of laser diodes is configured to operate
in a pulsed mode having a pulse repetition rate, and wherein the
infrared camera is configured to lock-in to the pulsed mode.
7. A smart phone or tablet, comprising: a first at least one of a
plurality of laser diodes, the first at least one of the plurality
of laser diodes configured to be pulsed; the plurality of laser
diodes configured to generate light having one or more optical
wavelengths, wherein at least a portion of the one or more optical
wavelengths is a near-infrared wavelength between 700 nanometers
and 2500 nanometers, and wherein at least a portion of the
plurality of laser diodes comprises one or more Bragg reflectors;
at least a portion of light from the plurality of laser diodes
capable of being directed to tissue comprising skin; a first laser
diode array configured to generate light having one or more optical
wavelengths, wherein at least a portion of the one or more optical
wavelengths is a near-infrared wavelength between 700 nanometers
and 2500 nanometers, and wherein at least a portion of the first
laser diode array comprises one or more Bragg reflectors; a second
laser diode array comprising a second at least one of the plurality
of laser diodes; an assembly in front of the first laser diode
array configured to receive at least a portion of the light from
the first laser diode array, the first laser diode array and the
assembly configured to form the light into a plurality of spots and
configured to direct at least some of the spots to the tissue; a
first receiver comprising a plurality of detectors; the first
receiver configured to receive at least a portion of light
reflected from the tissue from the first at least one of the
plurality of laser diodes; an infrared camera configured to receive
at least a portion of the light from the second laser diode array
reflected from the tissue, wherein the infrared camera generates
data based at least in part on the portion of the light received;
wherein the smart phone or tablet is configured to generate a
two-dimensional or three- dimensional image using at least part of
the data from the infrared camera.
8. The smart phone or tablet of claim 7, wherein the first receiver
is configured to perform a time-of-flight measurement by measuring
a time difference between the generated light from the first at
least one of the plurality of laser diodes and light reflected from
the tissue from the first at least one of the plurality of laser
diodes, and wherein the smart phone or tablet is configured to
receive and process at least a portion of the time-of-flight
measurement.
9. The smart phone or tablet of claim 8, wherein the plurality of
detectors comprise one or more detector arrays, and at least one of
the plurality of detectors is configured to receive at least a
portion of light from the first at least one of the plurality of
laser diodes and configured to generate a reference detector
output, and at least another of the plurality of detectors is
configured to receive at least a portion of light reflected from
the tissue from the first at least one of the plurality of laser
diodes and configured to generate a sample detector output, wherein
the first receiver is configured to generate a first receiver
output by comparing the reference detector output and the sample
detector output.
10. The smart phone or tablet of claim 9, wherein the second laser
diode array is also configured to be pulsed, and wherein the
infrared camera is configured to be synchronized to the second
laser diode array.
11. The smart phone or tablet of claim 10, wherein the first
receiver further comprises one or more filters in front of the one
or more detector arrays to select some of the one or more optical
wavelengths, wherein at least some of the plurality of laser diodes
operate near a 940 nanometer wavelength, and wherein the smart
phone or tablet is configured to process the two-dimensional or
three-dimensional image using a multivariate analysis.
12. The smart phone or tablet of claim 11, wherein the infrared
camera is further configured to: generate a first signal in
response to light received while the plurality of laser diodes and
the first laser diode array are off; and generate a second signal
in response to light received while at least one of the plurality
of laser diodes or at least one laser diode of the first laser
diode array is on, the received light including at least some light
from the at least one of the plurality of laser diodes reflected
from the tissue or at least some light from the first laser diode
array reflected from the tissue; wherein the smart phone or tablet
is further configured to use a difference between the first signal
and the second signal to, at least in part, generate the
two-dimensional or three-dimensional image.
13. The smart phone or tablet of claim 12, wherein the second laser
diode array is configured to operate in a pulsed mode having a
pulse repetition rate, and wherein the infrared camera is
configured to lock-in to the pulsed mode.
14. The smart phone or tablet of claim 13, wherein the
two-dimensional or three-dimensional image is used in part to
identify one or more features corresponding to the skin.
15. A smart phone or tablet, comprising: a first at least one of a
plurality of laser diodes configured to be operated in a pulsed
mode; a second at least one of the plurality of laser diodes also
configured to be operated in a pulsed mode; the plurality of laser
diodes configured to generate light having one or more optical
wavelengths, wherein at least a portion of the one or more optical
wavelengths is a near-infrared wavelength between 700 nanometers
and 2500 nanometers, and wherein at least one of the plurality of
laser diodes comprises one or more Bragg reflectors; at least a
portion of light from the plurality of laser diodes capable of
being directed to tissue comprising skin; an array of laser diodes
configured to generate light having one or more optical
wavelengths, wherein at least a portion of the one or more optical
wavelengths is a near-infrared wavelength between 700 nanometers
and 2500 nanometers, and wherein at least a portion of the array of
laser diodes comprises one or more Bragg reflectors; an assembly in
front of the array of laser diodes configured to receive at least a
portion of the light from the array of laser diodes, the array of
laser diodes and the assembly configured to form the light into a
plurality of spots and configured to direct at least some of the
spots to the tissue; a receiver comprising a plurality of
detectors; at least one of the plurality of detectors configured to
receive at least a portion of light from the first at least one of
the plurality of laser diodes and configured to generate a
reference detector output, and at least another of the plurality of
detectors configured to receive at least a portion of light
reflected from the tissue from the first at least one of the
plurality of laser diodes and configured to generate a sample
detector output, wherein the receiver is configured to generate a
first receiver output by comparing the reference detector output
and the sample detector output. the receiver further configured to
receive at least a portion of light reflected from the tissue from
the first at least one of the plurality of laser diodes, wherein
the receiver is configured to perform a time-of-flight measurement
by measuring a time difference between the generated light from the
first at least one of the plurality of laser diodes and light
reflected from the tissue from the first at least one of the
plurality of laser diodes, and wherein the receiver further
comprises one or more filters in front of at least one of the
plurality of detectors to select some of the one or more optical
wavelengths; an infrared camera configured to receive at least a
portion of the light from the second at least one of the plurality
of laser diodes reflected from the tissue, wherein the infrared
camera generates data based at least in part on the portion of the
light received; wherein the smart phone or tablet is configured to
receive and process at least a portion of the time-of-flight
measurement, and to generate a two-dimensional or three-dimensional
image using at least part of the data from the infrared camera.
16. The smart phone or tablet of claim 15, wherein the infrared
camera is configured to be synchronized to the second at least one
of the plurality of laser diodes, and wherein the smart phone or
tablet is configured to process the two-dimensional or
three-dimensional image using a multivariate analysis.
17. The smart phone or tablet of claim 16, wherein the second at
least one of the plurality of laser diodes configured to be
operated in a pulsed mode has a pulse repetition rate, and wherein
the infrared camera is configured to lock-in to the pulsed
mode.
18. The smart phone or tablet of claim 17, wherein the plurality of
detectors comprises one or more detector arrays, and wherein at
least a portion of the plurality of laser diodes operate near a 940
nanometer wavelength.
19. The smart phone or tablet of claim 18, wherein the infrared
camera is further configured to: generate a first signal in
response to light received while the plurality of laser diodes and
the array of laser diodes are off; and generate a second signal in
response to light received while the first or second at least one
of the plurality of laser diodes or at least one laser diode of the
array of laser diodes is on, the light received including at least
some light from the first or second at least one of the plurality
of laser diodes reflected from the tissue or at least some light
from the array of laser diodes reflected from the tissue; wherein
the smart phone or tablet is further configured to use a difference
between the first signal and the second signal to, at least in
part, generate the two-dimensional or three-dimensional image.
20. The smart phone or tablet of claim 19, wherein the
two-dimensional or three-dimensional image is used in part to
identify one or more features corresponding to the skin.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Continuation of U.S. application Ser.
No. 16/016,649 filed Jun. 24, 2018 (now U.S. Pat. No. 10,213,113),
which is a Continuation of U.S. application Ser. No. 15/860,065
filed Jan. 2, 2018 (now U.S. Pat. No. 10,098,546), which is a
Continuation of U.S. application Ser. No. 15/686,198 filed Aug. 25,
2017 (now U.S. Pat. No. 9,861,286), which is a Continuation of U.S.
application Ser. No. 15/357,136 filed Nov. 21, 2016 (now U.S. Pat.
No. 9,757,040), which is a Continuation of U.S. application Ser.
No. 14/651,367 filed Jun. 11, 2015 (now U.S. Pat. No. 9,500,635),
which is the U.S. national phase of PCT Application No.
PCT/US2013/075736 filed Dec. 17, 2013, which claims the benefit of
U.S. provisional application Ser. No. 61/747,477 filed Dec. 31,
2012 and U.S. provisional application Ser. No. 61/754,698 filed
Jan. 21, 2013, the disclosures of which are hereby incorporated by
reference in their entirety.
[0002] This application is related to U.S. provisional application
Ser. No. 61/747,472 filed Dec. 31, 2012; Ser. No. 61/747,481 filed
Dec. 31, 2012; Ser. No. 61/747,485 filed Dec. 31, 2012; Ser. No.
61/747,487 filed Dec. 31, 2012; Ser. No. 61/747,492 filed Dec. 31,
2012; and Ser. No. 61/747,553 filed Dec. 31, 2012, the disclosures
of which are hereby incorporated by reference in their entirety
herein.
[0003] This application has a common priority date with commonly
owned U.S. application Ser. No. 14/650,897 filed Jun. 10, 2015 (now
U.S. Pat. No. 9,494,567), which is the U.S. national phase of
International Application PCT/US2013/075700 entitled Near-Infrared
Lasers For Non-Invasive Monitoring Of Glucose, Ketones, HBA1C, And
Other Blood Constituents (Attorney Docket No. OMNI0101PCT); U.S.
application Ser. No. 14/108,995 filed Dec. 17, 2013 (published as
US 2014/0188092) entitled Focused Near-Infrared Lasers For
Non-Invasive Vasectomy And Other Thermal Coagulation Or Occlusion
Procedures (Attorney Docket No. OMNI0103PUSP); U.S. application
Ser. No. 14/650,981 filed Jun. 10, 2015 (now U.S. Pat. No.
9,500,634), which is the U.S. national phase of International
Application PCT/US2013/075767 entitled Short-Wave Infrared
Super-Continuum Lasers For Natural Gas Leak Detection, Exploration,
And Other Active Remote Sensing Applications (Attorney Docket No.
OMNI0104PCT); U.S. application Ser. No. 14/108,986 filed Dec. 17,
2013 (now U.S. Pat. No. 9,164,032) entitled Short-Wave Infrared
Super-Continuum Lasers For Detecting Counterfeit Or Illicit Drugs
And Pharmaceutical Process Control (Attorney Docket No.
OMNI0105PUSP); U.S. application Ser. No. 14/108,974 filed Dec. 17,
2013 (Published as US2014/0188094) entitled Non-Invasive Treatment
Of Varicose Veins (Attorney Docket No. OMNI0106PUSP); and U.S.
application Ser. No. 14/109,007 filed Dec. 17, 2013 (Published as
US2014/0236021) entitled Near-Infrared Super-Continuum Lasers For
Early Detection Of Breast And Other Cancers (Attorney Docket No.
OMNI0107PUSP), the disclosures of which are hereby incorporated in
their entirety by reference herein.
TECHNICAL FIELD
[0004] This disclosure relates to lasers and light sources for
healthcare, medical, dental, or bio-technology applications,
including systems and methods for using near-infrared or short-wave
infrared light sources for early detection of dental caries, often
called cavities.
BACKGROUND AND SUMMARY
[0005] Dental care and the prevention of dental decay or dental
caries has changed in the United States over the past several
decades, due to the introduction of fluoride to drinking water, the
use of fluoride dentifrices and rinses, application of topical
fluoride in the dental office, and improved dental hygiene. Despite
these advances, dental decay continues to be the leading cause of
tooth loss. With the improvements over the past several decades,
the majority of newly discovered carious lesions tend to be
localized to the occlusal pits and fissures of the posterior
dentition and the proximal contact sites. These early carious
lesions may be often obscured in the complex and convoluted
topography of the pits and fissures or may be concealed by debris
that frequently accumulates in those regions of the posterior
teeth. Moreover, such lesions are difficult to detect in the early
stages of development.
[0006] Dental caries may be a dynamic disease that is characterized
by tooth demineralization leading to an increase in the porosity of
the enamel surface. Leaving these lesions untreated may potentially
lead to cavities reaching the dentine and pulp and perhaps
eventually causing tooth loss. Occlusal surfaces (bite surfaces)
and approximal surfaces (between the teeth) are among the most
susceptible sites of demineralization due to acid attack from
bacterial by-products in the biofilm. Therefore, there is a need
for detection of lesions at an early stage, so that preventive
agents may be used to inhibit or reverse the demineralization.
[0007] Traditional methods for caries detection include visual
examination and tactile probing with a sharp dental exploration
tool, often assisted by radiographic (x-ray) imaging. However,
detection using these methods may be somewhat subjective; and, by
the time that caries are evident under visual and tactile
examination, the disease may have already progressed to an advanced
stage. Also, because of the ionizing nature of x-rays, they are
dangerous to use (limited use with adults, and even less used with
children). Although x-ray methods are suitable for approximal
surface lesion detection, they offer reduced utility for screening
early caries in occlusal surfaces due to their lack of sensitivity
at very early stages of the disease.
[0008] Some of the current imaging methods are based on the
observation of the changes of the light transport within the tooth,
namely absorption, scattering, transmission, reflection and/or
fluorescence of light. Porous media may scatter light more than
uniform media. Taking advantage of this effect, the Fiber-optic
trans-illumination is a qualitative method used to highlight the
lesions within teeth by observing the patterns formed when white
light, pumped from one side of the tooth, is scattered away and/or
absorbed by the lesion. This technique may be difficult to quantify
due to an uneven light distribution inside the tooth.
[0009] Another method called quantitative light-induced
fluorescence--QLF--relies on different fluorescence from solid
teeth and caries regions when excited with bright light in the
visible. For example, when excited by relatively high intensity
blue light, healthy tooth enamel yields a higher intensity of
fluorescence than does demineralized enamel that has been damaged
by caries infection or any other cause. On the other hand, for
excitation by relatively high intensity of red light, the opposite
magnitude change occurs, since this is the region of the spectrum
for which bacteria and bacterial by-products in carious regions
absorb and fluoresce more pronouncedly than do healthy areas.
However, the image provided by QLF may be difficult to assess due
to relatively poor contrast between healthy and infected areas.
Moreover, QLF may have difficulty discriminating between white
spots and stains because both produce similar effects. Stains on
teeth are commonly observed in the occlusal sites of teeth, and
this obscures the detection of caries using visible light.
[0010] As described in this disclosure, the near-infrared region of
the spectrum offers a novel approach to imaging carious regions
because scattering is reduced and absorption by stains is low. For
example, it has been demonstrated that the scattering by enamel
tissues reduces in the form of 1/(wavelength).sup.3, e.g.,
inversely as the cube of wavelength. By using a broadband light
source in the short-wave infrared (SWIR) part of the spectrum,
which corresponds approximately to 1400 nm to 2500 nm, lesions in
the enamel and dentine may be observed. In one embodiment, intact
teeth have low reflection over the SWIR wavelength range. In the
presence of caries, the scattering increases, and the scattering is
a function of wavelength; hence, the reflected signal decreases
with increasing wavelength. Moreover, particularly when caries
exist in the dentine region, water build up may occur, and dips in
the SWIR spectrum corresponding to the water absorption lines may
be observed. The scattering and water absorption as a function of
wavelength may thus be used for early detection of caries and for
quantifying the degree of demineralization.
[0011] SWIR light may be generated by light sources such as lamps,
light emitting diodes, one or more laser diodes, super-luminescent
laser diodes, and fiber-based super-continuum sources. The SWIR
super-continuum light sources advantageously may produce high
intensity and power, as well as being a nearly transform-limited
beam that may also be modulated. Also, apparatuses for caries
detection may include C-clamps over teeth, a handheld device with
light input and light detection, which may also be attached to
other dental equipment such as drills. Alternatively, a mouth-guard
type apparatus may be used to simultaneously illuminate one or more
teeth. Fiber optics may be conveniently used to guide the light to
the patient as well as to transport the signal back to one or more
detectors and receivers.
[0012] One approach to non-invasive monitoring of blood
constituents or blood analytes is to use near-infrared
spectroscopy, such as absorption spectroscopy or near-infrared
diffuse reflection or transmission spectroscopy. Some attempts have
been made to use broadband light sources, such as tungsten lamps,
to perform the spectroscopy. However, several challenges have
arisen in these efforts. First, many other constituents in the
blood also have signatures in the near-infrared, so spectroscopy
and pattern matching, often called spectral fingerprinting, is
required to distinguish the glucose with sufficient confidence.
Second, the non-invasive procedures have often transmitted or
reflected light through the skin, but skin has many spectral
artifacts in the near-infrared that may mask the glucose
signatures. Moreover, the skin may have significant water and blood
content. These difficulties become particularly complicated when a
weak light source is used, such as a lamp. More light intensity can
help to increase the signal levels, and, hence, the signal-to-noise
ratio.
[0013] In one embodiment, a wearable device includes a measurement
device including a light source comprising a plurality of light
emitting diodes (LEDs) for measuring one or more physiological
parameters, the measurement device configured to generate, by
modulating at least one of the LEDs having an initial light
intensity, an optical beam having a plurality of optical
wavelengths, wherein at least a portion of the plurality of optical
wavelengths is a near-infrared wavelength between 700 nanometers
and 2500 nanometers. The measurement device comprises one or more
lenses configured to receive and to deliver a portion of the
optical beam to tissue, wherein the tissue reflects at least a
portion of the optical beam delivered to the tissue, and wherein
the measurement device is adapted to be placed on a wrist or an ear
of a user. The measurement device further comprises a receiver, the
receiver having a plurality of spatially separated detectors and
one or more analog to digital converters coupled to the spatially
separated detectors, the one or more analog to digital converters
configured to generate at least two receiver outputs. The
measurement device is configured to improve a signal-to-noise ratio
of the optical beam reflected from the tissue by comparing the at
least two receiver outputs. The measurement device is also
configured to further improve the signal-to-noise ratio of the
optical beam reflected from the tissue by increasing the light
intensity relative to the initial light intensity from at least one
of the LEDs. The measurement device is further configured to
generate an output signal representing at least in part a
non-invasive measurement on blood contained within the tissue. The
receiver further comprises one or more spectral filters positioned
in front of at least some of the plurality of spatially separated
detectors, wherein the receiver is configured to be synchronized to
the modulation of the at least one of the LED, and wherein the
modulating at least one of the LEDs has a modulation frequency, and
wherein the receiver is configured to use a lock-in technique that
detects the modulation frequency.
[0014] In one or more embodiments, a wearable device comprises a
measurement device including a light source comprising a plurality
of light emitting diodes (LEDs) for measuring one or more
physiological parameters, the measurement device configured to
generate, by modulating at least one of the LEDs having an initial
light intensity, an optical beam having a plurality of optical
wavelengths, wherein at least a portion of the plurality of optical
wavelengths is a near-infrared wavelength between 700 nanometers
and 2500 nanometers. The measurement device comprises one or more
lenses configured to receive and to deliver a portion of the
optical beam to tissue, wherein the tissue reflects at least a
portion of the optical beam delivered to the tissue, and wherein
the measurement device is adapted to be placed on a wrist or an ear
of a user. The measurement device is configured to generate an
output signal representing at least in part a non-invasive
measurement on blood contained within the tissue. The measurement
device is configured to improve a signal-to-noise ratio of the
optical beam reflected from the tissue by increasing the light
intensity relative to the initial light intensity from at least one
of the LEDs. The measurement device further comprises a receiver
having one or more detectors, wherein one of the one or more
detectors is located a first distance from a first one of the LEDs
and a different distance from a second one of the LEDs such that
the receiver can compare light received from the first LED and
light received from the second LED, and wherein the output signal
is generated in part by comparing signals associated with the light
received from the first and second LEDs. The receiver is configured
to be synchronized to the modulation of the at least one of the
LEDs, wherein the modulating at least one of the LEDs has a
modulation frequency, and wherein the receiver is configured to use
a lock-in technique that detects the modulation frequency.
[0015] In at least one embodiment, a wearable device comprises a
measurement device including a light source comprising a plurality
of light emitting diodes (LEDs) for measuring one or more
physiological parameters, the measurement device configured to
generate, by modulating at least one of the LEDs having an initial
light intensity, an optical beam having a plurality of optical
wavelengths, wherein at least a portion of the plurality of optical
wavelengths is a near-infrared wavelength between 700 nanometers
and 2500 nanometers. The measurement device comprises one or more
lenses configured to receive and to deliver a portion of the
optical beam to tissue, wherein the tissue reflects at least a
portion of the optical beam delivered to the tissue, and wherein
the measurement device is adapted to be placed on a wrist or an ear
of a user. The measurement device is further configured to generate
an output signal representing at least in part a non-invasive
measurement on blood contained within the tissue. The measurement
device is configured to improve a signal-to-noise ratio of the
optical beam reflected from the tissue by increasing the light
intensity relative to the initial light intensity from at least one
of the LEDs. The measurement device further comprises a receiver,
the receiver having a plurality of spatially separated detectors
configured to generate at least two receiver outputs, and the
measurement device configured to further improve the
signal-to-noise ratio of the optical beam reflected from the tissue
by comparing the at least two receiver outputs. One of the
plurality of detectors is located a first distance from a first one
of the LEDs and a different distance from a second one of the LEDs
such that the receiver can generate a third signal responsive to
light received from the first LED and a fourth signal responsive to
light received from the second LED, and wherein the output signal
is generated in part by comparing the third and fourth signals,
wherein the receiver is configured to be synchronized to the
modulation of the at least one of the LEDs, and wherein the
modulating at least one of the LEDs has a modulation frequency, and
wherein the receiver is configured to use a lock-in technique that
detects the modulation frequency.
[0016] In one or more embodiments, a wearable device includes a
measurement device having a light source comprising a plurality of
light emitting diodes (LEDs) for measuring one or more
physiological parameters. The measurement device is configured to
generate, by modulating at least one of the LEDs having an initial
light intensity, an optical beam having a plurality of optical
wavelengths, wherein at least a portion of the optical beam
includes a near-infrared wavelength between 700 nanometers and 2500
nanometers. The measurement device comprises one or more lenses
configured to receive and to deliver at least a portion of the
optical beam to tissue, wherein the tissue reflects at least a
portion of the optical beam delivered to the tissue. The
measurement device further comprises a receiver having a plurality
of spatially separated detectors and one or more analog to digital
converters coupled to the spatially separated detectors, the one or
more analog to digital converters being configured to generate at
least two receiver outputs. The receiver is configured to capture
light while the LEDs are off and convert the captured light into a
first signal, and to capture light while at least one of the LEDs
is on and to convert the captured light into a second signal, the
captured light including at least a portion of the optical beam
reflected from the tissue. The measurement device is configured to
improve a signal-to-noise ratio of the optical beam reflected from
the tissue by differencing the first signal and the second signal
and by differencing the two receiver outputs. The measurement
device is configured to further improve the signal-to-noise ratio
of the optical beam reflected from the tissue by increasing the
light intensity relative to the initial light intensity from at
least one of the LEDs. The measurement device is further configured
to generate an output signal representing at least in part a
non-invasive measurement on blood contained within the tissue.
[0017] Embodiments may include a wearable device comprising a
measurement device including a light source comprising a plurality
of light emitting diodes (LEDs) for measuring one or more
physiological parameters. The measurement device is configured to
generate, by modulating at least one of the LEDs having an initial
light intensity, an optical beam having a plurality of optical
wavelengths, wherein at least a portion of the plurality of optical
wavelengths is a near-infrared wavelength between 700 nanometers
and 2500 nanometers. The measurement device comprises one or more
lenses configured to receive and to deliver a portion of the
optical beam to tissue, wherein the tissue reflects at least a
portion of the optical beam delivered to the tissue, and wherein
the measurement device is adapted to be placed on a wrist or an ear
of a user. The measurement device further comprises a receiver
having a plurality of spatially separated detectors and one or more
analog to digital converters coupled to the spatially separated
detectors. The one or more analog to digital converters is
configured to generate at least two receiver outputs. The receiver
is configured to capture light while the LEDs are off and convert
the captured light into a first signal, and to capture light while
at least one of the LEDs is on and convert the captured light into
a second signal, the captured light including at least a portion of
the optical beam reflected from the tissue. The measurement device
is configured to improve a signal-to-noise ratio of the optical
beam reflected from the tissue by differencing the first signal and
the second signal and by differencing the two receiver outputs. The
measurement device is also configured to further improve the
signal-to-noise ratio of the optical beam reflected from the tissue
by increasing the light intensity relative to the initial light
intensity from at least one of the LEDs. The measurement device is
further configured to generate an output signal representing at
least in part a non-invasive measurement on blood contained within
the tissue.
[0018] In one or more embodiments, a wearable device comprises a
measurement device including a light source comprising a plurality
of light emitting diodes (LEDs) for measuring one or more
physiological parameters. The measurement device is configured to
generate, by modulating at least one of the LEDs having an initial
light intensity, an optical beam having a plurality of optical
wavelengths, wherein at least a portion of the plurality of optical
wavelengths is a near-infrared wavelength between 700 nanometers
and 2500 nanometers. The measurement device comprises one or more
lenses configured to receive and to deliver a portion of the
optical beam to tissue, wherein the tissue reflects at least a
portion of the optical beam delivered to the tissue, and wherein
the measurement device is adapted to be placed on a wrist or an ear
of a user. The measurement device further comprises a receiver
having a plurality of spatially separated detectors and one or more
analog to digital converters coupled to the spatially separated
detectors, the one or more analog to digital converters configured
to generate at least two receiver outputs. The receiver is
configured to capture light while the LEDs are off and convert the
captured light into a first signal, and to capture light while at
least one of the LEDs is on and convert the captured light into a
second signal, the captured light including at least a portion of
the optical beam reflected from the tissue. The measurement device
is configured to improve a signal-to-noise ratio of the optical
beam reflected from the tissue by differencing the first signal and
the second signal and by differencing the two receiver outputs. The
measurement device is configured to further improve the
signal-to-noise ratio of the optical beam reflected from the tissue
by increasing the light intensity relative to the initial light
intensity from at least one of the LEDs. The measurement device is
further configured to generate an output signal representing at
least in part a non-invasive measurement on blood contained within
the tissue, wherein the output signal is generated at least in part
by using a Fourier transform and mathematical manipulation of a
signal resulting from the captured light. The receiver further
comprises one or more spectral filters positioned in front of at
least some of the plurality of spatially separated detectors.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] For a more complete understanding of the present disclosure,
and for further features and advantages thereof, reference is now
made to the following description taken in conjunction with the
accompanying drawings, in which:
[0020] FIG. 1 illustrates the structure of a tooth.
[0021] FIG. 2A shows the attenuation coefficient for dental enamel
and water versus wavelength from approximately 600 nm to 2600
nm.
[0022] FIG. 2B illustrates the absorption spectrum of intact enamel
and dentine in the wavelength range of approximately 1.2 to 2.4
microns.
[0023] FIG. 3 shows the near infrared spectral reflectance over the
wavelength range of approximately 800 nm to 2500 nm from an
occlusal tooth surface. The black diamonds correspond to the
reflectance from a sound, intact tooth section. The asterisks
correspond to a tooth section with an enamel lesion. The circles
correspond to a tooth section with a dentine lesion.
[0024] FIG. 4 illustrates a hand-held dental tool design of a human
interface that may also be coupled with other dental tools.
[0025] FIG. 5A illustrates a clamp design of a human interface to
cap over one or more teeth and perform a non-invasive measurement
for dental caries.
[0026] FIG. 5B shows a mouth guard design of a human interface to
perform a non-invasive measurement for dental caries.
[0027] FIG. 6A illustrates the dorsal of a hand for performing a
differential measurement for measuring blood constituents or
analytes.
[0028] FIG. 6B illustrates the dorsal of a foot for performing a
differential measurement for measuring blood constituents or
analytes.
[0029] FIG. 7 illustrates a block diagram or building blocks for
constructing high power laser diode assemblies.
[0030] FIG. 8 shows a platform architecture for different
wavelength ranges for an all-fiber-integrated, high powered,
super-continuum light source.
[0031] FIG. 9 illustrates one embodiment for a short-wave infrared
super-continuum light source.
[0032] FIG. 10 shows the output spectrum from the SWIR SC laser of
FIG. 9 when about 10 m length of fiber for SC generation is used.
This fiber is a single-mode, non-dispersion shifted fiber that is
optimized for operation near 1550 nm.
[0033] FIG. 11A illustrates a schematic of the experimental set-up
for measuring the diffuse reflectance spectroscopy using the
SWIR-SC light source of FIGS. 9 and 10.
[0034] FIG. 11B shows exemplary reflectance from a sound enamel
region, an enamel lesion region, and a dentine lesion region. The
spectra are normalized to have equal value near 2050 nm.
[0035] FIGS. 12A-B illustrate high power SWIR-SC lasers that may
generate light between approximately 1.4-1.8 microns (FIG. 12A) or
approximately 2-2.5 microns (FIG. 12B).
[0036] FIG. 12C shows a reflection-spectroscopy based stand-off
detection system having an SC laser source.
[0037] FIG. 12D shows one example of a dual-beam experimental
set-up that may be used to subtract out (or at least minimize the
adverse effects of) light source fluctuations.
[0038] FIG. 13 schematically shows that the medical measurement
device can be part of a personal or body area network that
communicates with another device (e.g., smart phone or tablet) that
communicates with the cloud. The cloud may in turn communicate
information with the user, dental or healthcare providers, or other
designated recipients.
[0039] FIG. 14A is a schematic diagram of the basic elements of an
imaging spectrometer.
[0040] FIG. 14B illustrates one example of a typical imaging
spectrometer used in hyper-spectral imaging systems.
DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS
[0041] As required, detailed embodiments of the present disclosure
are disclosed herein; however, it is to be understood that the
disclosed embodiments are merely exemplary of the disclosure that
may be embodied in various and alternative forms. The figures are
not necessarily to scale; some features may be exaggerated or
minimized to show details of particular components. Therefore,
specific structural and functional details disclosed herein are not
to be interpreted as limiting, but merely as a representative basis
for teaching one skilled in the art to variously employ the present
disclosure.
[0042] Near-infrared (NIR) and SWIR light may be preferred for
caries detection compared to visible light imaging because the
NIR/SWIR wavelengths generally have lower absorption by stains and
deeper penetration into teeth. Hence, NIR/SWIR light may provide a
caries detection method that can be non-invasive, non-contact and
relatively stain insensitive. Broadband light may provide further
advantages because carious regions may demonstrate spectral
signatures from water absorption and the wavelength dependence of
porosity in the scattering of light.
[0043] The wavelength of light should be selected appropriately to
achieve a non-invasive procedure. For example, the light should be
able to penetrate deep enough to reach through the dermis and
subcutaneous fat layers to reach varicose veins. For example, the
penetration depth may be defined as the inverse of the absorption
coefficient, although it may also be necessary to include the
scattering for the calculation. To achieve penetration deep enough
to reach the varicose veins, wavelengths may correspond to local
minima in water 501 and adipose 502 absorption, as well as
potentially local minima in collagen 503 and elastin 504
absorption. For example, wavelengths near approximately 1100 nm,
1310 nm, or 1650 nm may be advantageous for non-invasive
procedures. More generally, wavelength ranges of approximately 900
nm to 1150 nm, 1280 nm to 1340 nm, or 1550 nm to 1680 nm may be
advantageous for non-invasive procedures.
[0044] In general, the near-infrared region of the electromagnetic
spectrum covers between approximately 0.7 microns (700 nm) to about
2.5 microns (2500 nm). However, it may also be advantageous to use
just the short-wave infrared between approximately 1.4 microns
(1400 nm) and about 2.5 microns (2500 nm). One reason for
preferring the SWIR over the entire NIR may be to operate in the
so-called "eye safe" window, which corresponds to wavelengths
longer than about 1400 nm. Therefore, for the remainder of the
disclosure the SWIR will be used for illustrative purposes.
However, it should be clear that the discussion that follows could
also apply to using the NIR wavelength range, or other wavelength
bands.
[0045] In particular, wavelengths in the eye safe window may not
transmit down to the retina of the eye, and therefore, these
wavelengths may be less likely to create permanent eye damage from
inadvertent exposure. The near-infrared wavelengths have the
potential to be dangerous, because the eye cannot see the
wavelengths (as it can in the visible), yet they can penetrate and
cause damage to the eye. Even if a practitioner is not looking
directly at the laser beam, the practitioner's eyes may receive
stray light from a reflection or scattering from some surface.
Hence, it can always be a good practice to use eye protection when
working around lasers. Since wavelengths longer than about 1400 nm
are substantially not transmitted to the retina or substantially
absorbed in the retina, this wavelength range is known as the eye
safe window. For wavelengths longer than 1400 nm, in general only
the cornea of the eye may receive or absorb the light
radiation.
[0046] FIG. 1 illustrates the structure of an exemplary
cross-section of a tooth 100. The tooth 100 has a top layer called
the crown 101 and below that a root 102 that reaches well into the
gum 106 and bone 108 of the mouth. The exterior of the crown 101 is
an enamel layer 103, and below the enamel is a layer of dentine 104
that sits atop a layer of cementum 107. Below the dentine 104 is a
pulp region 105, which comprises within it blood vessels 109 and
nerves 110. If the light can penetrate the enamel 103 and dentine
104, then the blood flow and blood constituents may be measured
through the blood vessels in the dental pulp 105. While the amount
of blood flow in the capillaries of the dental pulp 105 may be less
than an artery or vein, the smaller blood flow could still be
advantageous for detecting or measuring blood constituents as
compared to detection through the skin if there is less interfering
spectral features from the tooth. Although the structure of a molar
tooth is illustrated in FIG. 1, other types of teeth also have
similar structure. For example, different types of teeth include
molars, pre-molars, canine and incisor teeth.
[0047] As used throughout this document, the term "couple" and or
"coupled" refers to any direct or indirect communication between
two or more elements, whether or not those elements are physically
connected to one another. As used throughout this disclosure, the
term "spectroscopy" means that a tissue or sample is inspected by
comparing different features, such as wavelength (or frequency),
spatial location, transmission, absorption, reflectivity,
scattering, refractive index, or opacity. In one embodiment,
"spectroscopy" may mean that the wavelength of the light source is
varied, and the transmission, absorption, or reflectivity of the
tissue or sample is measured as a function of wavelength. In
another embodiment, "spectroscopy" may mean that the wavelength
dependence of the transmission, absorption or reflectivity is
compared between different spatial locations on a tissue or sample.
As an illustration, the "spectroscopy" may be performed by varying
the wavelength of the light source, or by using a broadband light
source and analyzing the signal using a spectrometer, wavemeter, or
optical spectrum analyzer.
[0048] As used throughout this disclosure, the term "fiber laser"
refers to a laser or oscillator that has as an output light or an
optical beam, wherein at least a part of the laser comprises an
optical fiber. For instance, the fiber in the "fiber laser" may
comprise one of or a combination of a single mode fiber, a
multi-mode fiber, a mid-infrared fiber, a photonic crystal fiber, a
doped fiber, a gain fiber, or, more generally, an approximately
cylindrically shaped waveguide or light-pipe. In one embodiment,
the gain fiber may be doped with rare earth material, such as
ytterbium, erbium, and/or thulium, for example. In another
embodiment, the mid-infrared fiber may comprise one or a
combination of fluoride fiber, ZBLAN fiber, chalcogenide fiber,
tellurite fiber, or germanium doped fiber. In yet another
embodiment, the single mode fiber may include standard single-mode
fiber, dispersion shifted fiber, non-zero dispersion shifted fiber,
high-nonlinearity fiber, and small core size fibers.
[0049] As used throughout this disclosure, the term "pump laser"
refers to a laser or oscillator that has as an output light or an
optical beam, wherein the output light or optical beam is coupled
to a gain medium to excite the gain medium, which in turn may
amplify another input optical signal or beam. In one particular
example, the gain medium may be a doped fiber, such as a fiber
doped with ytterbium, erbium, and/or thulium. In one embodiment,
the "pump laser" may be a fiber laser, a solid state laser, a laser
involving a nonlinear crystal, an optical parametric oscillator, a
semiconductor laser, or a plurality of semiconductor lasers that
may be multiplexed together. In another embodiment, the "pump
laser" may be coupled to the gain medium by using a fiber coupler,
a dichroic mirror, a multiplexer, a wavelength division
multiplexer, a grating, or a fused fiber coupler.
[0050] As used throughout this document, the term "super-continuum"
and or "supercontinuum" and or "SC" refers to a broadband light
beam or output that comprises a plurality of wavelengths. In a
particular example, the plurality of wavelengths may be adjacent to
one-another, so that the spectrum of the light beam or output
appears as a continuous band when measured with a spectrometer. In
one embodiment, the broadband light beam may have a bandwidth or at
least 10 nm. In another embodiment, the "super-continuum" may be
generated through nonlinear optical interactions in a medium, such
as an optical fiber or nonlinear crystal. For example, the
"super-continuum" may be generated through one or a combination of
nonlinear activities such as four-wave mixing, the Raman effect,
modulational instability, and self-phase modulation.
[0051] As used throughout this disclosure, the terms "optical
light" and or "optical beam" and or "light beam" refer to photons
or light transmitted to a particular location in space. The
"optical light" and or "optical beam" and or "light beam" may be
modulated or unmodulated, which also means that they may or may not
contain information. In one embodiment, the "optical light" and or
"optical beam" and or "light beam" may originate from a fiber, a
fiber laser, a laser, a light emitting diode, a lamp, a pump laser,
or a light source.
Transmission or Reflection Through Teeth
[0052] The transmission, absorption and reflection from teeth has
been studied in the near infrared, and, although there are some
features, the enamel and dentine appear to be fairly transparent in
the near infrared (particularly SWIR wavelengths between about 1400
and 2500 nm). For example, the absorption or extinction ratio for
light transmission has been studied. FIG. 2A illustrates the
attenuation coefficient 200 for dental enamel 201 (filled circles)
and the absorption coefficient of water 202 (open circles) versus
wavelength. Near-infrared light may penetrate much further without
scattering through all the tooth enamel, due to the reduced
scattering coefficient in normal enamel. Scattering in enamel may
be fairly strong in the visible, but decreases as approximately
1/(wavelength).sup.3 [i.e., inverse of the cube of the wavelength]
with increasing wavelength to a value of only 2-3 cm-1 at 1310 nm
and 1550 nm in the near infrared. Therefore, enamel may be
virtually transparent in the near infrared with optical attenuation
1-2 orders of magnitude less than in the visible range.
[0053] As another example, FIG. 2B illustrates the absorption
spectrum 250 of intact enamel 251 (dashed line) and dentine 252
(solid line) in the wavelength range of approximately 1.2 to 2.4
microns. In the near infrared there are two absorption bands in the
areas of about 1.5 and 2 microns. The band with a peak around 1.57
microns may be attributed to the overtone of valent vibration of
water present in both enamel and dentine. In this band, the
absorption is greater for dentine than for enamel, which may be
related to the large water content in this tissue. In the region of
2 microns, dentine may have two absorption bands, and enamel one.
The band with a maximum near 2.1 microns may belong to the overtone
of vibration of PO hydroxyapatite groups, which is the main
substance of both enamel and dentine. Moreover, the band with a
peak near 1.96 microns in dentine may correspond to water
absorption (dentine may contain substantially higher water than
enamel).
[0054] In addition to the absorption coefficient, the reflectance
from intact teeth and teeth with dental caries (e.g., cavities) has
been studied. In one embodiment, FIG. 3 shows the near infrared
spectral reflectance 300 over the wavelength range of approximately
800 nm to 2500 nm from an occlusal (e.g., top) tooth surface 304.
The curve with black diamonds 301 corresponds to the reflectance
from a sound, intact tooth section. The curve with asterisks (*)
302 corresponds to a tooth section with an enamel lesion. The curve
with circles 303 corresponds to a tooth section with a dentine
lesion. Thus, when there is a lesion, more scattering occurs and
there may be an increase in the reflected light.
[0055] For wavelengths shorter than approximately 1400 nm, the
shapes of the spectra remain similar, but the amplitude of the
reflection changes with lesions. Between approximately 1400 nm and
2500 nm, an intact tooth 301 has low reflectance (e.g., high
transmission), and the reflectance appears to be more or less
independent of wavelength. On the other hand, in the presence of
lesions 302 and 303, there is increased scattering, and the
scattering loss may be wavelength dependent. For example, the
scattering loss may decrease as the inverse of some power of
wavelength, such as 1/(wavelength).sup.3--so, the scattering loss
decreases with longer wavelengths. When there is a lesion in the
dentine 303, more water can accumulate in the area, so there is
also increased water absorption. For example, the dips near 1450 nm
and 1900 nm may correspond to water absorption, and the reflectance
dips are particularly pronounced in the dentine lesion 303.
[0056] FIG. 3 may point to several novel techniques for early
detection and quantification of carious regions. One method may be
to use a relatively narrow wavelength range (for example, from a
laser diode or super-luminescent laser diode) in the wavelength
window below 1400 nm. In one embodiment, wavelengths in the
vicinity of 1310 nm may be used, which is a standard
telecommunications wavelength where appropriate light sources are
available. Also, it may be advantageous to use a super-luminescent
laser diode rather than a laser diode, because the broader
bandwidth may avoid the production of laser speckle that can
produce interference patterns due to light's scattering after
striking irregular surfaces. As FIG. 3 shows, the amplitude of the
reflected light (which may also be proportional to the inverse of
the transmission) may increase with dental caries. Hence, comparing
the reflected light from a known intact region with a suspect
region may help identify carious regions. However, one difficulty
with using a relatively narrow wavelength range and relying on
amplitude changes may be the calibration of the measurement. For
example, the amplitude of the reflected light may depend on many
factors, such as irregularities in the dental surface, placement of
the light source and detector, distance of the measurement
instrument from the tooth, etc.
[0057] In one embodiment, use of a plurality of wavelengths can
help to better calibrate the dental caries measurement. For
example, a plurality of laser diodes or super-luminescent laser
diodes may be used at different center wavelengths. Alternately, a
lamp or alternate broadband light source may be used followed by
appropriate filters, which may be placed after the light source or
before the detectors. In one example, wavelengths near 1090 nm,
1440 nm and 1610 nm may be employed. The reflection from the tooth
305 appears to reach a local maximum near 1090 nm in the
representative embodiment illustrated. Also, the reflectance near
1440 nm 306 is higher for dental caries, with a distinct dip
particularly for dentine caries 303. Near 1610 nm 307, the
reflection is also higher for carious regions. By using a plurality
of wavelengths, the values at different wavelengths may help
quantify a caries score. In one embodiment, the degree of enamel
lesions may be proportional to the ratio of the reflectance near
1610 nm divided by the reflectance near 1090 nm. Also, the degree
of dentine lesion may be proportional to the difference between the
reflectance near 1610 nm and 1440 nm, with the difference then
divided by the reflectance near 1090 nm. Although one set of
wavelengths has been described, other wavelengths may also be used
and are intended to be covered by this disclosure.
[0058] In yet another embodiment, it may be further advantageous to
use all of some fraction of the SWIR between approximately 1400 and
2500 nm. For example, a SWIR super-continuum light source could be
used, or a lamp source could be used. On the receiver side, a
spectrometer and/or dispersive element could be used to
discriminate the various wavelengths. As FIG. 3 shows, an intact
tooth 301 has a relatively low and featureless reflectance over the
SWIR. On the other hand, with a carious region there is more
scattering, so the reflectance 302, 303 increases in amplitude.
Since the scattering is inversely proportional to wavelength or
some power of wavelength, the carious region reflectance 302, 303
also decreases with increasing wavelength. Moreover, the carious
region may contain more water, so there are dips in the reflectance
near the water absorption lines 306 and 308. The degree of caries
or caries score may be quantified by the shape of the spectrum over
the SWIR, taking ratios of different parts of the spectrum, or some
combination of this and other spectral processing methods.
[0059] Although several methods of early caries detection using
spectral reflectance have been described, other techniques could
also be used and are intended to be covered by this disclosure. For
example, transmittance may be used rather than reflectance, or a
combination of the two could be used. Moreover, the transmittance,
reflectance and/or absorbance could also be combined with other
techniques, such as quantitative light-induced fluorescence or
fiber-optic trans-illumination. Also, the SWIR could be
advantageous, but other parts of the infrared, near-infrared or
visible wavelengths may also be used consistent with this
disclosure.
[0060] One other benefit of the absorption, transmission or
reflectance in the near infrared and SWIR may be that stains and
non-calcified plaque are not visible in this wavelength range,
enabling better discrimination of defects, cracks, and
demineralized areas. For example, dental calculus, accumulated
plaque, and organic stains and debris may interfere significantly
with visual diagnosis and fluorescence-based caries detection
schemes in occlusal surfaces. In the case of using quantitative
light-induced fluorescence, such confounding factors typically may
need to be removed by prophylaxis (abrasive cleaning) before
reliable measurements can be taken. Surface staining at visible
wavelengths may further complicate the problem, and it may be
difficult to determine whether pits and fissures are simply stained
or demineralized. On the other hand, staining and pigmentation
generally interfere less with NIR or SWIR imaging. For example, NIR
and SWIR light may not be absorbed by melanin and porphyrins
produced by bacteria and those found in food dyes that accumulate
in dental plaque and are responsible for the pigmentation.
Human Interface for Measurement System
[0061] A number of different types of measurements may be used to
image for dental caries, particularly early detection of dental
caries. A basic feature of the measurements may be that the optical
properties are measured as a function of wavelength at a plurality
of wavelengths. As further described below, the light source may
output a plurality of wavelengths, or a continuous spectrum over a
range of wavelengths. In one embodiment, the light source may cover
some or all of the wavelength range between approximately 1400 nm
and 2500 nm. The signal may be received at a receiver, which may
also comprise a spectrometer or filters to discriminate between
different wavelengths. The signal may also be received at a camera,
which may also comprise filters or a spectrometer. In one
embodiment, the spectral discrimination using filters or a
spectrometer may be placed after the light source rather than at
the receiver. The receiver usually comprises one or more detectors
(optical-to-electrical conversion element) and electrical
circuitry. The receiver may also be coupled to analog to digital
converters, particularly if the signal is to be fed to a digital
device.
[0062] Referring to FIG. 1, one or more light sources 111 may be
used for illumination. In one embodiment, a transmission
measurement may be performed by directing the light source output
111 to the region near the interface between the gum 106 and
dentine 104. In one embodiment, the light may be directed using a
light guide or a fiber optic. The light may then propagate through
the dental pulp 105 to the other side, where the light may be
incident on one or more detectors or another light guide to
transport the signal to 112 a spectrometer, receiver, and/or
camera, for example. In one embodiment, the light source may be
directed to one or more locations near the interface between the
gum 106 and dentine 104 (in one example, could be from the two
sides of the tooth). The transmitted light may then be detected in
the occlusal surface above the tooth using a 112 spectrometer,
receiver, or camera, for example. In another embodiment, a
reflectance measurement may be conducted by directing the light
source output 111 to, for example, the occlusal surface of the
tooth, and then detecting the reflectance at a 113 spectrometer,
receiver or camera. Although a few embodiments for imaging the
tooth are described, other embodiments and techniques may also be
used and are intended to be covered by this disclosure. These
optical techniques may measure optical properties such as
reflectance, transmittance, absorption, or luminescence.
[0063] In one embodiment, FIG. 4 shows that the light source and/or
detection system may be integrated with a dental hand-piece 400.
The hand-piece 400 may also include other dental equipment, such as
a drill, pick, air spray or water cooling stream. The dental
hand-piece 400 may include a housing 401 and a motor housing 402
(in some embodiments such as with a drill, a motor may be placed in
this section). The end of hand-piece 403 that interfaces with the
tooth may be detachable, and it may also have the light input and
output end. The dental hand-piece 400 may also have an umbilical
cord 404 for connecting to power supplies, diagnostics, or other
equipment, for example.
[0064] A light guide 405 may be integrated with the hand-piece 400,
either inside the housing 401, 402 or adjacent to the housing. In
one embodiment, a light source 410 may be contained within the
housing 401, 402. In an alternative embodiment, the hand-piece 400
may have a coupler 410 to couple to an external light source 411
and/or detection system or receiver 412. The light source 411 may
be coupled to the hand-piece 400 using a light guide or fiber optic
cable 406. In addition, the detection system or receiver 412 may be
coupled to the hand-piece 400 using one or more light guides, fiber
optic cable or a bundle of fibers 407.
[0065] The light incident on the tooth may exit the hand-piece 400
through the end 403. The end 403 may also have a lens system or
curved mirror system to collimate or focus the light. In one
embodiment, if the light source is integrated with a tool such as a
drill, then the light may reach the tooth at the same point as the
tip of the drill. The reflected or transmitted light from the tooth
may then be observed externally and/or guided back through the
light guide 405 in the hand-piece 400. If observed externally,
there may be a lens system 408 for collecting the light and a
detection system 409 that may have one or more detectors and
electronics. If the light is to be guided back through the
hand-piece 400, then the reflected light may transmit through the
light guide 405 back to the detection system or receiver 412. In
one embodiment, the incident light may be guided by a fiber optic
through the light guide 405, and the reflected light may be
captured by a series of fibers forming a bundle adjacent to or
surrounding the incident light fiber.
[0066] In another embodiment, a "clamp" design 500 may be used as a
cap over one or more teeth, as illustrated in FIG. 5A. The clamp
design may be different for different types of teeth, or it may be
flexible enough to fit over different types of teeth. For example,
different types of teeth include the molars (toward the back of the
mouth), the premolars, the canine, and the incisors (toward the
front of the mouth). One embodiment of the clamp-type design is
illustrated in FIG. 5A for a molar tooth 508. The C-clamp 501 may
be made of a plastic or rubber material, and it may comprise a
light source input 502 and a detector output 503 on the front or
back of the tooth, for example.
[0067] The light source input 502 may comprise a light source
directly, or it may have light guided to it from an external light
source. Also, the light source input 502 may comprise a lens system
to collimate or focus the light across the tooth. The detector
output 503 may comprise a detector directly, or it may have a light
guide to transport the signal to an external detector element. The
light source input 502 may be coupled electrically or optically
through 504 to a light input 506. For example, if the light source
is external in 506, then the coupling element 504 may be a light
guide, such as a fiber optic. Alternately, if the light source is
contained in 502, then the coupling element 504 may be electrical
wires connecting to a power supply in 506. Similarly, the detector
output 503 may be coupled to a detector output unit 507 with a
coupling element 505, which may be one or more electrical wires or
a light guide, such as a fiber optic. This is just one example of a
clamp over one or more teeth, but other embodiments may also be
used and are intended to be covered by this disclosure. For
example, if reflectance from the teeth is to be used in the
measurement, then the light input 502 and detected light input 503
may be on the same side of the tooth.
[0068] In yet another embodiment, one or more light source ports
and sensor ports may be used in a mouth-guard type design. For
example, one embodiment of a dental mouth guard 550 is illustrated
in FIG. 5B. The structure of the mouth guard 551 may be similar to
mouth guards used in sports (e.g., when playing football or boxing)
or in dental trays used for applying fluoride treatment, and the
mouth guard may be made from plastic, rubber, or any other suitable
materials. As an example, the mouth guard may have one or more
light source input ports 552, 553 and one or more detector output
ports 554, 555. Although six input and output ports are
illustrated, any number of ports may be used.
[0069] Similar to the clamp design described above, the light
source inputs 552, 553 may comprise one or more light sources
directly, or they may have light guided to them from an external
light source. Also, the light source inputs 552, 553 may comprise
lens systems to collimate or focus the light across the teeth. The
detector outputs 554, 555 may comprise one or more detectors
directly, or they may have one or more light guides to transport
the signals to an external detector element. The light source
inputs 552, 553 may be coupled electrically or optically through
556 to a light input 557. For example, if the light source is
external in 557, then the one or more coupling elements 556 may be
one or more light guides, such as a fiber optic. Alternately, if
the light sources are contained in 552, 553, then the coupling
element 556 may be one or more electrical wires connecting to a
power supply in 557. Similarly, the detector outputs 554, 555 may
be coupled to a detector output unit 559 with one or more coupling
elements 558, which may be one or more electrical wires or one or
more light guides, such as a fiber optic. This is just one example
of a mouth guard design covering a plurality of teeth, but other
embodiments may also be used and are intended to be covered by this
disclosure. For instance, the position of the light source inputs
and detector output ports could be exchanged, or some mixture of
locations of light source inputs and detector output ports could be
used. Also, if reflectance from the teeth is to be measured, then
the light sources and detectors may be on the same side of the
tooth. Moreover, it may be advantageous to pulse the light source
with a particular pulse width and pulse repetition rate, and then
the detection system can measure the pulsed light returned from or
transmitted through the tooth. Using a lock-in type technique
(e.g., detecting at the same frequency as the pulsed light source
and also possibly phase locked to the same signal), the detection
system may be able to reject background or spurious signals and
increase the signal-to-noise ratio of the measurement.
[0070] Other elements may be added to the human interface designs
of FIGS. 4-6 and are also intended to be covered by this
disclosure. For instance, in one embodiment it may be desirable to
have replaceable inserts that may be disposable. Particularly in a
dentist's or doctor's office or hospital setting, the same
instrument may be used with a plurality of patients. Rather than
disinfecting the human interface after each use, it may be
preferable to have disposable inserts that can be thrown away after
each use. In one embodiment, a thin plastic coating material may
enclose the clamp design of FIG. 5A or mouth guard design of FIG.
5B. The coating material may be inserted before each use, and then
after the measurement is exercised the coating material may be
peeled off and replaced. The coating or covering material may be
selected based on suitable optical properties that do not affect
the measurement, or known optical properties that can be calibrated
or compensated for during measurement. Such a design may save the
dentist or physician or user considerable time, while at the same
time provide the business venture with a recurring cost revenue
source.
[0071] Thus, beyond the problem of other blood constituents or
analytes having overlapping spectral features, it may be difficult
to observe glucose spectral signatures through the skin and its
constituents of water, adipose, collagen and elastin. One approach
to overcoming this difficulty may be to try to measure the blood
constituents in veins that are located at relatively shallow
distances below the skin. Veins may be more beneficial for the
measurement than arteries, since arteries tend to be located at
deeper levels below the skin. Also, in one embodiment it may be
advantageous to use a differential measurement to subtract out some
of the interfering absorption lines from the skin. For example, an
instrument head may be designed to place one probe above a region
of skin over a blood vein, while a second probe may be placed at a
region of the skin without a noticeable blood vein below it. Then,
by differencing the signals from the two probes, at least part of
the skin interference may be cancelled out.
[0072] Two representative embodiments for performing such a
differential measurement are illustrated in FIG. 6A and FIG. 6B. In
one embodiment shown in FIG. 6A, the dorsal of the hand 600 may be
used for measuring blood constituents or analytes. The dorsal of
the hand 600 may have regions that have distinct veins 601 as well
as regions where the veins are not as shallow or pronounced 602. By
stretching the hand and leaning it backwards, the veins 601 may be
accentuated in some cases. A near-infrared diffuse reflectance
measurement may be performed by placing one probe 603 above the
vein-rich region 601. To turn this into a differential measurement,
a second probe 604 may be placed above a region without distinct
veins 602. Then, the outputs from the two probes may be subtracted
605 to at least partially cancel out the features from the skin.
The subtraction may be done preferably in the electrical domain,
although it can also be performed in the optical domain or
digitally/mathematically using sampled data based on the electrical
and/or optical signals. Although one example of using the dorsal of
the hand 600 is shown, many other parts of the hand can be used
within the scope of this disclosure. For example, alternate methods
may use transmission through the webbing between the thumb and the
fingers 606, or transmission or diffuse reflection through the tips
of the fingers 607.
[0073] In another embodiment, the dorsal of the foot 650 may be
used instead of the hand. One advantage of such a configuration may
be that for self-testing by a user, the foot may be easier to
position the instrument using both hands. One probe 653 may be
placed over regions where there are more distinct veins 651, and a
near-infrared diffuse reflectance measurement may be made. For a
differential measurement, a second probe 654 may be placed over a
region with less prominent veins 652, and then the two probe
signals may be subtracted, either electronically or optically, or
may be digitized/sampled and processed mathematically depending on
the particular application and implementation. As with the hand,
the differential measurements may be intended to compensate for or
subtract out (at least in part) the interference from the skin.
Since two regions are used in close proximity on the same body
part, this may also aid in removing some variability in the skin
from environmental effects such as temperature, humidity, or
pressure. In addition, it may be advantageous to first treat the
skin before the measurement, by perhaps wiping with a cloth or
treated cotton ball, applying some sort of cream, or placing an ice
cube or chilled bag over the region of interest.
[0074] Although two embodiments have been described, many other
locations on the body may be used using a single or differential
probe within the scope of this disclosure. In yet another
embodiment, the wrist may be advantageously used, particularly
where a pulse rate is typically monitored. Since the pulse may be
easily felt on the wrist, there is underlying the region a distinct
blood flow. Other embodiments may use other parts of the body, such
as the ear lobes, the tongue, the inner lip, the nails, the eye, or
the teeth. Some of these embodiments will be further described
below. The ear lobes or the tip of the tongue may be advantageous
because they are thinner skin regions, thus permitting transmission
rather than diffuse reflection. However, the interference from the
skin is still a problem in these embodiments. Other regions such as
the inner lip or the bottom of the tongue may be contemplated
because distinct veins are observable, but still the interference
from the skin may be problematic in these embodiments. The eye may
seem as a viable alternative because it is more transparent than
skin. However, there are still issues with scattering in the eye.
For example, the anterior chamber of the eye (the space between the
cornea and the iris) comprises a fluid known as aqueous humor.
However, the glucose level in the eye chamber may have a
significant temporal lag on changes in the glucose level compared
to the blood glucose level.
[0075] One of the issues in measuring a particular blood
constituent is the interfering and overlapping signal from other
blood constituents. The selection of the constituent of interest
may be improved using a number of techniques. For example, a higher
light level or intensity may improve the signal-to-noise ratio for
the measurement. Second, mathematical modeling and signal
processing methodologies may help to reduce the interference, such
as multivariate techniques, multiple linear regression, and
factor-based algorithms, for example. For instance, a number of
mathematical approaches include multiple linear regression, partial
least squares, and principal component regression (PCR). Various
mathematical derivatives, including the first and second
derivatives, may help to accentuate differences between spectra. In
addition, by using a wider wavelength range and using more sampling
wavelengths may improve the ability to discriminate one signal from
another. These are just examples of some of the methods of
improving the ability to discriminate between different
constituents, but other techniques may also be used and are
intended to be covered by this disclosure.
Light Sources for Near Infrared
[0076] There are a number of light sources that may be used in the
near infrared. To be more specific, the discussion below will
consider light sources operating in the short wave infrared (SWIR),
which may cover the wavelength range of approximately 1400 nm to
2500 nm. Other wavelength ranges may also be used for the
applications described in this disclosure, so the discussion below
is merely provided as exemplary types of light sources. The SWIR
wavelength range may be valuable for a number of reasons. First,
the SWIR corresponds to a transmission window through water and the
atmosphere. Second, the so-called "eye-safe" wavelengths are
wavelengths longer than approximately 1400 nm. Third, the SWIR
covers the wavelength range for nonlinear combinations of
stretching and bending modes as well as the first overtone of C--H
stretching modes. Thus, for example, glucose and ketones among
other substances may have unique signatures in the SWIR. Moreover,
many solids have distinct spectral signatures in the SWIR, so
particular solids may be identified using stand-off detection or
remote sensing. For instance, many explosives have unique
signatures in the SWIR.
[0077] Different light sources may be selected for the SWIR based
on the needs of the application. Some of the features for selecting
a particular light source include power or intensity, wavelength
range or bandwidth, spatial or temporal coherence, spatial beam
quality for focusing or transmission over long distance, and pulse
width or pulse repetition rate. Depending on the application,
lamps, light emitting diodes (LEDs), laser diodes (LD's), tunable
LD's, super-luminescent laser diodes (SLDs), fiber lasers or
super-continuum sources (SC) may be advantageously used. Also,
different fibers may be used for transporting the light, such as
fused silica fibers, plastic fibers, mid-infrared fibers (e.g.,
tellurite, chalcogenides, fluorides, ZBLAN, etc), or a hybrid of
these fibers.
[0078] Lamps may be used if low power or intensity of light is
required in the SWIR, and if an incoherent beam is suitable. In one
embodiment, in the SWIR an incandescent lamp that can be used is
based on tungsten and halogen, which have an emission wavelength
between approximately 500 nm to 2500 nm. For low intensity
applications, it may also be possible to use thermal sources, where
the SWIR radiation is based on the black body radiation from the
hot object. Although the thermal and lamp based sources are
broadband and have low intensity fluctuations, it may be difficult
to achieve a high signal-to-noise ratio due to the low power
levels. Also, the lamp based sources tend to be energy
inefficient.
[0079] In another embodiment, LED's can be used that have a higher
power level in the SWIR wavelength range. LED' s also produce an
incoherent beam, but the power level can be higher than a lamp and
with higher energy efficiency. Also, the LED output may more easily
be modulated, and the LED provides the option of continuous wave or
pulsed mode of operation. LED' s are solid state components that
emit a wavelength band that is of moderate width, typically between
about 20 nm to 40 nm. There are also so-called super-luminescent
LEDs that may even emit over a much wider wavelength range. In
another embodiment, a wide band light source may be constructed by
combining different LEDs that emit in different wavelength bands,
some of which could preferably overlap in spectrum. One advantage
of LEDs as well as other solid state components is the compact size
that they may be packaged into.
[0080] In yet another embodiment, various types of laser diodes may
be used in the SWIR wavelength range. Just as LEDs may be higher in
power but narrower in wavelength emission than lamps and thermal
sources, the LDs may be yet higher in power but yet narrower in
wavelength emission than LEDs. Different kinds of LDs may be used,
including Fabry-Perot LDs, distributed feedback (DFB) LDs,
distributed Bragg reflector (DBR) LDs. Since the LDs have
relatively narrow wavelength range (typically under 10 nm), in one
embodiment a plurality of LDs may be used that are at different
wavelengths in the SWIR. The various LDs may be spatially
multiplexed, polarization multiplexed, wavelength multiplexed, or a
combination of these multiplexing methods. Also, the LDs may be
fiber pig-tailed or have one or more lenses on the output to
collimate or focus the light. Another advantage of LDs is that they
may be packaged compactly and may have a spatially coherent beam
output. Moreover, tunable LDs that can tune over a range of
wavelengths are also available. The tuning may be done by varying
the temperature, or electrical current may be used in particular
structures such as distributed Bragg reflector (DBR) LDs, for
example. In another embodiment, external cavity LDs may be used
that have a tuning element, such as a fiber grating or a bulk
grating, in the external cavity.
[0081] In another embodiment, super-luminescent laser diodes may
provide higher power as well as broad bandwidth. An SLD is
typically an edge emitting semiconductor light source based on
super-luminescence (e.g., this could be amplified spontaneous
emission). SLDs combine the higher power and brightness of LDs with
the low coherence of conventional LEDs, and the emission band for
SLD' s may be 5 to 100 nm wide, preferably in the 60 to 100 nm
range. Although currently SLDs are commercially available in the
wavelength range of approximately 400 nm to 1700 nm, SLDs could and
may in the future be made to cover a broader region of the
SWIR.
[0082] In yet another embodiment, high power LDs for either direct
excitation or to pump fiber lasers and SC light sources may be
constructed using one or more laser diode bar stacks. FIG. 7 shows
an example of a block diagram 700 or building blocks for
constructing the high power LDs. In this embodiment, one or more
diode bar stacks 701 may be used, where the diode bar stack may be
an array of several single emitter LDs. Since the fast axis (e.g.,
vertical direction) may be nearly diffraction limited while the
slow-axis (e.g., horizontal axis) may be far from diffraction
limited, different collimators 702 may be used for the two
axes.
[0083] Then, the brightness may be increased by spatially combining
the beams from multiple stacks 703. The combiner may include
spatial interleaving, it may include wavelength multiplexing, or it
may involve a combination of the two. Different spatial
interleaving schemes may be used, such as using an array of prisms
or mirrors with spacers to bend one array of beams into the beam
path of the other. In another embodiment, segmented mirrors with
alternate high-reflection and anti-reflection coatings may be used.
Moreover, the brightness may be increased by polarization beam
combining 704 the two orthogonal polarizations, such as by using a
polarization beam splitter. In a particular embodiment, the output
may then be focused or coupled into a large diameter core fiber. As
an example, typical dimensions for the large diameter core fiber
range from diameters of approximately 100 microns to 400 microns or
more. Alternatively or in addition, a custom beam shaping module
705 may be used, depending on the particular application. For
example, the output of the high power LD may be used directly 706,
or it may be fiber coupled 707 to combine, integrate, or transport
the high power LD energy. These high power LDs may grow in
importance because the LD powers can rapidly scale up. For example,
instead of the power being limited by the power available from a
single emitter, the power may increase in multiples depending on
the number of diodes multiplexed and the size of the large diameter
fiber. Although FIG. 7 is shown as one embodiment, some or all of
the elements may be used in a high power LD, or additional elements
may also be used.
[0084] As described in greater detail in commonly owned US Pat.
App. Pub. 2014/0188094, in some instances, it may be desirable to
create multiple locations of focused light. For example, the speed
of the treatment for varicose veins may be increased by causing
thermal coagulation or occlusion at multiple locations. Multiple
collimated or focused light beams may be created in one assembly.
In such embodiments, optionally a surface cooling apparatus may be
used, where a cooling fluid may be flowed either touching or in
close proximity to the skin. Also, in this particular embodiment a
cylindrical assembly may optionally be used, where the cylindrical
length may be several millimeters in length and defined by a clamp
or mount placed on or near the leg. In one embodiment, a window
and/or lenslet array is also shown on the cylindrical surface for
permitting the light to be incident on the skin and varicose vein
at multiple spots. The lenslet array may comprise circular,
spherical or cylindrical lenses, depending on the type of spots
desired. As before, one advantage of placing the lenslet array in
close proximity to the skin and varicose vein may be that a high NA
lens may be used. Also, the input from the lens and/or mirror
assembly to the lenslet array may be single large beam, or a
plurality of smaller beams. In one embodiment, a plurality of spots
may be created by the lenslet array to cause a plurality of
locations of thermal coagulation in the varicose vein. Any number
of spots may be used and are intended to be covered by this
disclosure.
[0085] In a non-limiting example, a plurality of spots may be used,
or what might be called a fractionated beam. The fractionated laser
beam may be added to the laser delivery assembly or delivery head
in a number of ways. In one embodiment, a screen-like spatial
filter may be placed in the pathway of the beam to be delivered to
the biological tissue. The screen-like spatial filter can have
opaque regions to block the light and holes or transparent regions,
through which the laser beam may pass to the tissue sample. The
ratio of opaque to transparent regions may be varied, depending on
the application of the laser. In another embodiment, a lenslet
array can be used at or near the output interface where the light
emerges. In yet another embodiment, at least a part of the delivery
fiber from the infrared laser system to the delivery head may be a
bundle of fibers, which may comprise a plurality of fiber cores
surrounded by cladding regions. The fiber cores can then correspond
to the exposed regions, and the cladding areas can approximate the
opaque areas not to be exposed to the laser light. As an example, a
bundle of fibers may be excited by at least a part of the laser
system output, and then the fiber bundle can be fused together and
perhaps pulled down to a desired diameter to expose to the tissue
sample near the delivery head. In yet another embodiment, a
photonic crystal fiber may be used to create the fractionated laser
beam. In one non-limiting example, the photonic crystal fiber can
be coupled to at least a part of the laser system output at one
end, and the other end can be coupled to the delivery head. In a
further example, the fractionated laser beam may be generated by a
heavily multi-mode fiber, where the speckle pattern at the output
may create the high intensity and low intensity spatial pattern at
the output. Although several exemplary techniques are provided for
creating a fractionated laser beam, other techniques that can be
compatible with optical fibers are also intended to be included by
this disclosure.
[0086] Although the output from a fiber laser may be from a single
or multi-mode fiber, different spatial spot sizes or spatial
profiles may be beneficial for different applications. For example,
in some instances it may be desirable to have a series of spots or
a fractionated beam with a grid of spots. In one embodiment, a
bundle of fibers or a light pipe with a plurality of guiding cores
may be used. In another embodiment, one or more fiber cores may be
followed by a lenslet array to create a plurality of collimated or
focused beams. In yet another embodiment, a delivery light pipe may
be followed by a grid-like structure to divide up the beam into a
plurality of spots. These are specific examples of beam shaping,
and other apparatuses and methods may also be used and are
consistent with this disclosure.
SWIR Super-Continuum Lasers
[0087] Each of the light sources described above have particular
strengths, but they also may have limitations. For example, there
is typically a trade-off between wavelength range and power output.
Also, sources such as lamps, thermal sources, and LEDs produce
incoherent beams that may be difficult to focus to a small area and
may have difficulty propagating for long distances. An alternative
source that may overcome some of these limitations is an SC light
source. Some of the advantages of the SC source may include high
power and intensity, wide bandwidth, spatially coherent beam that
can propagate nearly transform limited over long distances, and
easy compatibility with fiber delivery.
[0088] Supercontinuum lasers may combine the broadband attributes
of lamps with the spatial coherence and high brightness of lasers.
By exploiting a modulational instability initiated supercontinuum
(SC) mechanism, an all-fiber-integrated SC laser with no moving
parts may be built using commercial-off-the-shelf (COTS)
components. Moreover, the fiber laser architecture may be a
platform where SC in the visible, near-infrared/SWIR, or mid-IR can
be generated by appropriate selection of the amplifier technology
and the SC generation fiber. But until recently, SC lasers were
used primarily in laboratory settings since typically large,
table-top, mode-locked lasers were used to pump nonlinear media
such as optical fibers to generate SC light. However, those large
pump lasers may now be replaced with diode lasers and fiber
amplifiers that gained maturity in the telecommunications
industry.
[0089] In one embodiment, an all-fiber-integrated, high-powered SC
light source 800 may be elegant for its simplicity (FIG. 8). The
light may be first generated from a seed laser diode 801. For
example, the seed LD 801 may be a distributed feedback (DFB) laser
diode with a wavelength near 1542 or 1550 nm, with approximately
0.5-2.0 ns pulsed output, and with a pulse repetition rate between
about one kilohertz to about 100 MHz or more. The output from the
seed laser diode may then be amplified in a multiple-stage fiber
amplifier 802 comprising one or more gain fiber segments. In one
embodiment, the first stage pre-amplifier 803 may be designed for
optimal noise performance. For example, the pre-amplifier 803 may
be a standard erbium-doped fiber amplifier or an erbium/ytterbium
doped cladding pumped fiber amplifier. Between amplifier stages 803
and 806, it may be advantageous to use band-pass filters 804 to
block amplified spontaneous emission and isolators 805 to prevent
spurious reflections. Then, the power amplifier stage 806 may use a
cladding-pumped fiber amplifier that may be optimized to minimize
nonlinear distortion. The power amplifier fiber 806 may also be an
erbium-doped fiber amplifier, if only low or moderate power levels
are to be generated.
[0090] The SC generation 807 may occur in the relatively short
lengths of fiber that follow the pump laser. The SC fiber length
may range from around a few millimeters to 100 m or more. In one
embodiment, the SC generation may occur in a first fiber 808 where
the modulational-instability initiated pulse break-up occurs
primarily, followed by a second fiber 809 where the SC generation
and spectral broadening occurs primarily.
[0091] In one embodiment, one or two meters of standard single-mode
fiber (SMF) after the power amplifier stage may be followed by
several meters of SC generation fiber. For this example, in the SMF
the peak power may be several kilowatts and the pump light may fall
in the anomalous group-velocity dispersion regime--often called the
soliton regime. For high peak powers in the anomalous dispersion
regime, the nanosecond pulses may be unstable due to a phenomenon
known as modulational instability, which is basically parametric
amplification in which the fiber nonlinearity helps to phase match
the pulses. As a consequence, the nanosecond pump pulses may be
broken into many shorter pulses as the modulational instability
tries to form soliton pulses from the quasi-continuous-wave
background. Although the laser diode and amplification process
starts with approximately nanosecond-long pulses, modulational
instability in the short length of SMF fiber may form approximately
0.5 ps to several-picosecond-long pulses with high intensity. Thus,
the few meters of SMF fiber may result in an output similar to that
produced by mode-locked lasers, except in a much simpler and
cost-effective manner.
[0092] The short pulses created through modulational instability
may then be coupled into a nonlinear fiber for SC generation. The
nonlinear mechanisms leading to broadband SC may include four-wave
mixing or self-phase modulation along with the optical Raman
effect. Since the Raman effect is self-phase-matched and shifts
light to longer wavelengths by emission of optical photons, the SC
may spread to longer wavelengths very efficiently. The
short-wavelength edge may arise from four-wave mixing, and often
times the short wavelength edge may be limited by increasing
group-velocity dispersion in the fiber. In many instances, if the
particular fiber used has sufficient peak power and SC fiber
length, the SC generation process may fill the long-wavelength edge
up to the transmission window.
[0093] Mature fiber amplifiers for the power amplifier stage 806
include ytterbium-doped fibers (near 1060 nm), erbium-doped fibers
(near 1550 nm), erbium/ytterbium-doped fibers (near 1550 nm), or
thulium-doped fibers (near 2000 nm). In various embodiments,
candidates for SC fiber 809 include fused silica fibers (for
generating SC between 0.8-2.7 .mu.m), mid-IR fibers such as
fluorides, chalcogenides, or tellurites (for generating SC out to
4.5 .mu.m or longer), photonic crystal fibers (for generating SC
between 0.4 and 1.7 .mu.m), or combinations of these fibers.
Therefore, by selecting the appropriate fiber-amplifier doping for
806 and nonlinear fiber 809, SC may be generated in the visible,
near-IR/SWIR, or mid-IR wavelength region.
[0094] The configuration 800 of FIG. 8 is just one particular
example, and other configurations can be used and are intended to
be covered by this disclosure. For example, further gain stages may
be used, and different types of lossy elements or fiber taps may be
used between the amplifier stages. In another embodiment, the SC
generation may occur partially in the amplifier fiber and in the
pig-tails from the pump combiner or other elements. In yet another
embodiment, polarization maintaining fibers may be used, and a
polarizer may also be used to enhance the polarization contrast
between amplifier stages. Also, not discussed in detail are many
accessories that may accompany this set-up, such as driver
electronics, pump laser diodes, safety shut-offs, and thermal
management and packaging.
[0095] In one embodiment, one example of the SC laser that operates
in the SWIR is illustrated in FIG. 9. This SWIR SC source 900
produces an output of up to approximately 5W over a spectral range
of about 1.5 to 2.4 microns, and this particular laser is made out
of polarization maintaining components. The seed laser 901 is a
distributed feedback (DFB) laser operating near 1542 nm producing
approximately 0.5 nsec pulses at an about 8 MHz repetition rate.
The pre-amplifier 902 is forward pumped and uses about 2 m length
of erbium/ytterbium cladding pumped fiber 903 (often also called
dual-core fiber)with an inner core diameter of 12 microns and outer
core diameter of 130 microns. The pre-amplifier gain fiber 903 is
pumped using a 10W laser diode near 940 nm 905 that is coupled in
using a fiber combiner 904.
[0096] In this particular 5W unit, the mid-stage between amplifier
stages 902 and 906 comprises an isolator 907, a band-pass filter
908, a polarizer 909 and a fiber tap 910. The power amplifier 906
uses an approximately 4 m length of the 12/130 micron
erbium/ytterbium doped fiber 911 that is counter-propagating pumped
using one or more 30W laser diodes near 940 nm 912 coupled in
through a combiner 913. An approximately 1-2 meter length of the
combiner pig-tail helps to initiate the SC process, and then a
length of PM-1550 fiber 915 (polarization maintaining, single-mode,
fused silica fiber optimized for 1550 nm) is spliced 914 to the
combiner output.
[0097] If an output fiber of about 10 m in length is used, then the
resulting output spectrum 1000 is shown in FIG. 10. The details of
the output spectrum 1000 depend on the peak power into the fiber,
the fiber length, and properties of the fiber such as length and
core size, as well as the zero dispersion wavelength and the
dispersion properties. For example, if a shorter length of fiber is
used, then the spectrum actually reaches to longer wavelengths
(e.g., a 2 m length of SC fiber broadens the spectrum to about 2500
nm). Also, if extra-dry fibers are used with less O--H content,
then the wavelength edge may also reach to a longer wavelength. To
generate more spectra toward the shorter wavelengths, the pump
wavelength (in this case .about.1542 nm) should be close to the
zero dispersion wavelength in the fiber. For example, by using a
dispersion shifted fiber or so-called non-zero dispersion shifted
fiber, the short wavelength edge may shift to shorter
wavelengths.
[0098] In one particular embodiment, the SWIR-SC light source of
FIG. 9 with output spectrum in FIG. 10 was used in preliminary
experiments for examining the reflectance from different dental
samples. A schematic of the experimental set-up 1100 for measuring
the diffuse reflectance spectroscopy is illustrated in FIG. 11A.
The SC source 1101 in this embodiment was based on the design of
FIG. 9 and delivered approximately 1.6W of light over the
wavelength range from about 1500-2400 nm. The output beam 1102 was
collimated, and then passed through a chopper 1103 (for lock-in
detection at the receiver after the spectrometer 1106) and an
aperture 1104 for localizing the beam on the tooth location.
Different teeth 1105 with different lesions and caries were placed
in front of the aperture 1104, and the scattered light was passed
through a spectrometer 1106 and collected on a detector, whose
signal was sent to a receiver. The tooth samples 1105 were mounted
in clay or putty for standing upright. Different types of teeth
could be used, including molars, premolars, canine and incisor
teeth.
[0099] FIG. 11B shows exemplary reflectance spectra 1150 from a
sound enamel region 1151 (e.g., without dental caries), an enamel
lesion region 1152, and a dentine lesion region 1153 of various
teeth. The spectra are normalized to have equal value near 2050 nm.
In this particular embodiment, the slope from the sound enamel 1151
is steepest between about 1500 and 1950 nm, with a lesser slope in
the presence of an enamel lesion 1152. When there is a sample with
dentine lesion 1153, more features appear in the spectrum from the
presence of water absorption lines from water that collects in the
dentine. For this experiment, the spectra 1151, 1152, and 1153 are
flatter in the wavelength region between about 1950 nm and 2350 nm.
These are preliminary results, but they show the benefit of using
broadband sources such as the SWIR-SC source for diagnosing dental
caries. Although the explanation behind the different spectra 1150
of FIG. 11B may not be understood as yet, it is clear that the
spectra 1151, 1152 and 1153 are distinguishable. Therefore, the
broadband reflectance may be used for detection of dental caries
and analyzing the region of the caries. Although diffuse
reflectance has been used in this experiment, other signals, such
as transmission, reflectance or a combination, may also be used and
are covered by this disclosure.
[0100] Although one particular example of a 5W SWIR-SC has been
described, different components, different fibers, and different
configurations may also be used consistent with this disclosure.
For instance, another embodiment of the similar configuration 900
in FIG. 9 may be used to generate high powered SC between
approximately 1060 and 1800 nm. For this embodiment, the seed laser
901 may be a distributed feedback laser diode of about 1064 nm, the
pre-amplifier gain fiber 903 may be a ytterbium-doped fiber
amplifier with 10/125 microns dimensions, and the pump laser 905
may be a 10W laser diode near 915 nm. A mode field adapter may be
including in the mid-stage, in addition to the isolator 907, band
pass filter 908, polarizer 909 and tap 910. The gain fiber 911 in
the power amplifier may be an about 20 m length of ytterbium-doped
fiber with 25/400 microns dimension. The pump 912 for the power
amplifier may be up to six pump diodes providing 30W each near 915
nm. For this much pump power, the output power in the SC may be as
high as 50W or more.
[0101] In an alternate embodiment, it may be desirous to generate
high power SWIR SC over 1.4-1.8 microns and separately 2-2.5
microns (the window between 1.8 and 2 microns may be less important
due to the strong water and atmospheric absorption). For example,
the SC source of FIG. 12A can lead to bandwidths ranging from about
1400 nm to 1800 nm or broader, while the SC source of FIG. 12B can
lead to bandwidths ranging from about 1900 nm to 2500 nm or
broader. Since these wavelength ranges are shorter than about 2500
nm, the SC fiber can be based on fused silica fiber. Exemplary SC
fibers include standard single-mode fiber (SMF), high-nonlinearity
fiber, high-NA fiber, dispersion shifted fiber, dispersion
compensating fiber, and photonic crystal fibers. Non-fused-silica
fibers can also be used for SC generation, including chalcogenides,
fluorides, ZBLAN, tellurites, and germanium oxide fibers.
[0102] In one embodiment, FIG. 12A illustrates a block diagram for
an SC source 1200 capable of generating light between approximately
1400 nm and 1800 nm or broader. As an example, a pump fiber laser
similar to FIG. 9 can be used as the input to a SC fiber 1209. The
seed laser diode 1201 can comprise a DFB laser that generates, for
example, several milliwatts of power around 1542 nm or 1553 nm. The
fiber pre-amplifier 1202 can comprise an erbium-doped fiber
amplifier or an erbium/ytterbium doped double clad fiber. In this
example, a mid-stage amplifier 1203 can be used, which can comprise
an erbium/ytterbium doped double-clad fiber. A bandpass filter 1205
and isolator 1206 may be used between the pre-amplifier 1202 and
mid-stage amplifier 1203. The power amplifier stage 1204 can
comprise a larger core size erbium/ytterbium doped double-clad
fiber, and another bandpass filter 1207 and isolator 1208 can be
used before the power amplifier 1204. The output of the power
amplifier can be coupled to the SC fiber 1209 to generate the SC
output 1210. This is just one exemplary configuration for an SC
source, and other configurations or elements may be used consistent
with this disclosure.
[0103] In yet another embodiment, FIG. 12B illustrates a block
diagram for an SC source 1250 capable of generating light between
approximately 1900 and 2500 nm or broader. As an example, the seed
laser diode 1251 can comprise a DFB or DBR laser that generates,
for example, several milliwatts of power around 1542 nm or 1553 nm.
The fiber pre-amplifier 1252 can comprise an erbium-doped fiber
amplifier or an erbium/ytterbium doped double-clad fiber. In this
example, a mid-stage amplifier 1253 can be used, which can comprise
an erbium/ytterbium doped double-clad fiber. A bandpass filter 1255
and isolator 1256 may be used between the pre-amplifier 1252 and
mid-stage amplifier 1253. The power amplifier stage 1254 can
comprise a thulium doped double-clad fiber, and another isolator
1257 can be used before the power amplifier 1254. Note that the
output of the mid-stage amplifier 1253 can be approximately near
1542 nm, while the thulium-doped fiber amplifier 1254 can amplify
wavelengths longer than approximately 1900 nm and out to about 2100
nm. Therefore, for this configuration wavelength shifting may be
required between 1253 and 1254. In one embodiment, the wavelength
shifting can be accomplished using a length of standard single-mode
fiber 1258, which can have a length between approximately 5 and 50
meters, for example. The output of the power amplifier 1254 can be
coupled to the SC fiber 1259 to generate the SC output 1260. This
is just one exemplary configuration for an SC source, and other
configurations or elements can be used consistent with this
disclosure. For example, the various amplifier stages can comprise
different amplifier types, such as erbium doped fibers, ytterbium
doped fibers, erbium/ytterbium co-doped fibers and thulium doped
fibers.
[0104] FIG. 12C illustrates a reflection-spectroscopy based
stand-off detection system having an SC laser source. The set-up
1270 for the reflection-spectroscopy-based stand-off detection
system includes an SC source 1271. First, the diverging SC output
is collimated to a 1 cm diameter beam using a 25 mm focal length,
90 degrees off-axis, gold coated, parabolic mirror 1272. To reduce
the effects of chromatic aberration, refractive optics are avoided
in the setup. All focusing and collimation is done using metallic
mirrors that have almost constant reflectivity and focal length
over the entire SC output spectrum. The sample 1274 is kept at a
distance from the collimating mirror 1272, which provides a total
round trip path length of twice the distance before reaching the
collection optics 1275. A 12 cm diameter silver coated concave
mirror 1275 with a 75 cm focal length is kept 20 cm to the side of
the collimation mirror 1272. The mirror 1275 is used to collect a
fraction of the diffusely reflected light from the sample, and
focus it into the input slit of a monochromator 1276. Thus, the
beam is incident normally on the sample 1274, but detected at a
reflection angle of tan.sup.-1(0.2/5) or about 2.3 degrees.
Appropriate long wavelength pass filters mounted in a motorized
rotating filter wheel are placed in the beam path before the input
slit 1276 to avoid contribution from higher wavelength orders from
the grating (300 grooves/mm, 2 .mu.m blaze). The output slit width
is set to 2 mm corresponding to a spectral resolution of 10.8 nm,
and the light is detected by a 2 mm.times.2 mm liquid nitrogen
cooled (77K) indium antimonide (InSb) detector 1277. The detected
output is amplified using a trans-impedance pre-amplifier 1277 with
a gain of about 105V/A and connected to a lock-in amplifier 1278
setup for high sensitivity detection. The chopper frequency is 400
Hz, and the lock-in time constant is set to 100 ms corresponding to
a noise bandwidth of about 1 Hz. These are exemplary elements and
parameter values, but other or different optical elements may be
used consistent with this disclosure.
[0105] While the above detection systems could be categorized as
single path detection systems, it may be advantageous in some cases
to use multi-path detection systems. In one embodiment, a detection
system from a Fourier transform infrared spectrometer, FTIR, may be
used. The received light may be incident on a particular
configuration of mirrors, called a Michelson interferometer, that
allows some wavelengths to pass through but blocks others due to
wave interference. The beam may be modified for each new data point
by moving one of the mirrors, which changes the set of wavelengths
that pass through. This collected data is called an interferogram.
The interferogram is then processed, typically on a computing
system, using an algorithm called the Fourier transform. One
advantageous feature of FTIR is that it may simultaneously collect
spectral data in a wide spectral range.
[0106] Another advantage of using the near-infrared or SWIR is that
most drug packaging materials are at least partially transparent in
this wavelength range, so that drug compositions may be detected
and identified through the packaging non-destructively. As an
example, SWIR light could be used to see through plastics, since
the signature for plastics can be subtracted off and there are
large wavelength windows where the plastics are transparent.
Because of the hydro-carbon bonds, there are absorption features
near 1.7 microns and 2.2-2.5 microns. In general, the absorption
bands in the near infrared are due to overtones and combination
bands for various functional group vibrations, including signals
from C--H, O--H, C=O, N--H, --COOH, and aromatic C--H groups. It
may be difficult to assign an absorption band to a specific
functional group due to overlapping of several combinations and
overtones. However, with advancements in computational power and
chemometrics or multivariate analysis methods, complex systems may
be better analyzed. In one embodiment, using software analysis
tools the absorption spectrum may be converted to its second
derivative equivalent. The spectral differences may permit a fast,
accurate, non-destructive and reliable identification of materials.
Although particular derivatives are discussed, other mathematical
manipulations may be used in the analysis, and these other
techniques are also intended to be covered by this disclosure.
[0107] Described herein are just some examples of the beneficial
use of near-infrared or SWIR lasers for spectroscopy, active remote
sensing or hyper-spectral imaging. However, many other spectroscopy
and identification procedures can use the near-infrared or SWIR
light consistent with this disclosure and are intended to be
covered by the disclosure. As one example, the fiber-based
super-continuum lasers may have a pulsed output with pulse
durations of approximately 0.5-2 nsec and pulse repetition rates of
several Megahertz. Therefore, the near-infrared or SWIR
spectroscopy, active remote sensing or hyper-spectral imaging
applications may also be combined with LIDAR-type applications.
Namely, the distance or time axis can be added to the information
based on time-of-flight measurements. For this type of information
to be used, the detection system would also have to be time-gated
to be able to measure the time difference between the pulses sent
and the pulses received. By calculating the round-trip time for the
signal, the distance of the object may be judged. In another
embodiment, GPS (global positioning system) information may be
added, so the near-infrared or SWIR spectroscopy, active remote
sensing or hyper-spectral imagery would also have a location tag on
the data. Moreover, the near-infrared or SWIR spectroscopy, active
remote sensing or hyper-spectral imaging information could also be
combined with two-dimensional or three-dimensional images to
provide a physical picture as well as a chemical composition
identification of the materials. These are just some modifications
of the near-infrared or SWIR spectroscopy, active remote sensing or
hyper-spectral imaging system described in this disclosure, but
other techniques may also be added or combinations of these
techniques may be added, and these are also intended to be covered
by this disclosure.
[0108] In yet another example of multi-beam detection systems, a
dual-beam set-up 1280 such as in FIG. 12D may be used to subtract
out (or at least minimize the adverse effects of) light source
fluctuations. In one embodiment, the output from an SC source 1281
may be collimated using a CaF2 lens 1282 and then focused into the
entrance slit of the monochromator 1283. At the exit slit, light at
the selected wavelength is collimated again and may be passed
through a polarizer 1284 before being incident on a calcium
fluoride beam splitter 1285. After passing through the beam
splitter 1285, the light is split into a sample 1286 and reference
1287 arm to enable ratiometric detection that may cancel out
effects of intensity fluctuations in the SC source 1281. The light
in the sample arm 1286 passes through the sample of interest and is
then focused onto a HgCdTe detector 1288 connected to a pre-amp. A
chopper 1282 and lock-in amplifier 1290 setup enable low noise
detection of the sample arm signal. The light in the reference arm
1287 passes through an empty container (cuvette, gas cell etc.) of
the same kind as used in the sample arm. A substantially identical
detector 1289, pre-amp and lock-in amplifier 1290 is used for
detection of the reference arm signal. The signal may then be
analyzed using a computer system 1291. This is one particular
example of a method to remove fluctuations from the light source,
but other components may be added and other configurations may be
used, and these are also intended to be covered by this
disclosure.
[0109] Although particular examples of detection systems have been
described, combinations of these systems or other systems may also
be used, and these are also within the scope of this disclosure. As
one example, environmental fluctuations (such as turbulence or
winds) may lead to fluctuations in the beam for active remote
sensing or hyper-spectral imaging. A configuration such as FIG. 12D
may be able to remove the effect of environmental fluctuations. Yet
another technique may be to "wobble" the light beam after the light
source using a vibrating mirror. The motion may lead to the beam
moving enough to wash out spatial fluctuations within the beam
waist at the sample or detection system. If the vibrating mirror is
scanned faster than the integration time of the detectors, then the
spatial fluctuations in the beam may be integrated out.
Alternately, some sort of synchronous detection system may be used,
where the detection is synchronized to the vibrating frequency.
[0110] By use of an active illuminator, a number of advantages may
be achieved, such as higher signal-to-noise ratios. For example,
one way to improve the signal-to-noise ratio would be to use
modulation and lock-in techniques. In one embodiment, the light
source may be modulated, and then the detection system would be
synchronized with the light source. In a particular embodiment, the
techniques from lock-in detection may be used, where narrow band
filtering around the modulation frequency may be used to reject
noise outside the modulation frequency. In an alternate embodiment,
change detection schemes may be used, where the detection system
captures the signal with the light source on and with the light
source off. Again, for this system the light source may be
modulated. Then, the signal with and without the light source is
differenced. This may enable the sun light changes to be subtracted
out. In addition, change detection may help to identify objects
that change in the field of view. In the following some exemplary
detection systems are described.
[0111] In one embodiment, a SWIR camera or infrared camera system
may be used to capture the images. The camera may include one or
more lenses on the input, which may be adjustable. The focal plane
assemblies may be made from mercury cadmium telluride material
(HgCdTe), and the detectors may also include thermo-electric
coolers. Alternately, the image sensors may be made from indium
gallium arsenide (InGaAs), and CMOS transistors may be connected to
each pixel of the InGaAs photodiode array. The camera may interface
wirelessly or with a cable (e.g., USB, Ethernet cable, or fiber
optics cable) to a computer or tablet or smart phone, where the
images may be captured and processed. These are a few examples of
infrared cameras, but other SWIR or infrared cameras may be used
and are intended to be covered by this disclosure.
[0112] In another embodiment, an imaging spectrometer may be used
to detect the light received from the sample. For example, FIG. 14A
shows a schematic diagram 1400 of the basic elements of an imaging
spectrometer. The input light 1401 from the sample may first be
directed by a scanning mirror and/or other optics 1402. An optical
dispersing element 1403, such as a grating or prism, in the
spectrometer may split the light into many narrow, adjacent
wavelength bands, which may then be passed through imaging optics
1404 onto one or more detectors or detector arrays 1405. Some
sensors may use multiple detector arrays to measure hundreds of
narrow wavelength bands.
[0113] An example of a typical imaging spectrometer 1450 used in
hyper-spectral imaging systems is illustrated in FIG. 14B. In this
particular embodiment, the input light may be directed first by a
tunable mirror 1451. A front lens 1452 may be placed before the
entrance slit 1453 and the collector lens 1454. In this embodiment,
the dispersing element is a holographic grating with a prism 1455,
which separates the different wavelength bands. Then, a camera lens
1456 may be used to image the wavelengths onto a detector or camera
1457.
[0114] FIGS. 14A and 14B provide particular examples, but some of
the elements may not be used, or other elements may be added, and
these are also intended to be covered by this disclosure. For
instance, a scanning spectrometer may be used before the detector,
where a grating or dispersive element is scanned to vary the
wavelength being measured by the detector. In yet another
embodiment, filters may be used before one or more detectors to
select the wavelengths or wavelength bands to be measured. This may
be particularly useful if only a few bands or wavelengths are to be
measured. The filters may be dielectric filters, Fabry-Perot
filters, absorption or reflection filters, fiber gratings, or any
other wavelength selective filter. In one embodiment, a wavelength
division multiplexer, WDM, may be used followed by one or more
detectors or detector arrays. One example of a planar wavelength
division multiplexer may be a waveguide grating router or an
arrayed waveguide grating. The WDM may be fiber coupled, and
detectors may be placed directly at the output or the detectors may
be coupled through fibers to the WDM. Some of these components may
also be combined with the configurations in FIGS. 14A and 14B.
[0115] One advantage of the SC lasers illustrated is that they may
use all-fiber components, so that the SC laser can be all-fiber,
monolithically integrated with no moving parts. The all-integrated
configuration can consequently be robust and reliable.
[0116] The Figures provide examples of SC light sources that may
advantageously be used for SWIR light generation in various medical
and dental diagnostic and therapeutic applications. However, many
other versions of the SC light sources may also be made that are
intended to also be covered by this disclosure. For example, the SC
generation fiber could be pumped by a mode-locked laser, a
gain-switched semiconductor laser, an optically pumped
semiconductor laser, a solid state laser, other fiber lasers, or a
combination of these types of lasers. Also, rather than using a
fiber for SC generation, either a liquid or a gas cell might be
used as the nonlinear medium in which the spectrum is to be
broadened.
[0117] Even within the all-fiber versions illustrated such as in
FIG. 9, different configurations could be used consistent with the
disclosure. In an alternate embodiment, it may be desirous to have
a lower cost version of the SWIR SC laser of FIG. 9. One way to
lower the cost could be to use a single stage of optical
amplification, rather than two stages, which may be feasible if
lower output power is required or the gain fiber is optimized. For
example, the pre-amplifier stage 902 might be removed, along with
at least some of the mid-stage elements. In yet another embodiment,
the gain fiber could be double passed to emulate a two stage
amplifier. In this example, the pre-amplifier stage 902 might be
removed, and perhaps also some of the mid-stage elements. A mirror
or fiber grating reflector could be placed after the power
amplifier stage 906 that may preferentially reflect light near the
wavelength of the seed laser 901. If the mirror or fiber grating
reflector can transmit the pump light near 940 nm, then this could
also be used instead of the pump combiner 913 to bring in the pump
light 912. The SC fiber 915 could be placed between the seed laser
901 and the power amplifier stage 906 (SC is only generated after
the second pass through the amplifier, since the power level may be
sufficiently high at that time). In addition, an output coupler may
be placed between the seed laser diode 901 and the SC fiber, which
now may be in front of the power amplifier 906. In a particular
embodiment, the output coupler could be a power coupler or divider,
a dichroic coupler (e.g., passing seed laser wavelength but
outputting the SC wavelengths), or a wavelength division
multiplexer coupler. This is just one further example, but a myriad
of other combinations of components and architectures could also be
used for SC light sources to generate SWIR light that are intended
to be covered by this disclosure.
Wireless Link to the Cloud
[0118] The non-invasive dental caries measurement device may also
benefit from communicating the data output to the "cloud" (e.g.,
data servers and processors in the web remotely connected) via
wireless means. The non-invasive devices may be part of a series of
biosensors applied to the patient, and collectively these devices
form what might be called a body area network or a personal area
network. The biosensors and non-invasive devices may communicate to
a smart phone, tablet, personal data assistant, computer and/or
other microprocessor-based device, which may in turn wirelessly or
over wire and/or fiber optic transmit some or all of the signal or
processed data to the internet or cloud. The cloud or internet may
in turn send the data to dentists, doctors or health care providers
as well as the patients themselves. Thus, it may be possible to
have a panoramic, high-definition, relatively comprehensive view of
a patient that doctors and dentists can use to assess and manage
disease, and that patients can use to help maintain their health
and direct their own care.
[0119] In a particular embodiment 1300, the non-invasive
measurement device 1301 may comprise a transmitter 1303 to
communicate over a first communication link 1304 in the body area
network or personal area network to a receiver in a smart phone,
tablet, cell phone, PDA, and/or computer 1305, for example. For the
measurement device 1301, it may also be advantageous to have a
processor 1302 to process some of the measured data, since with
processing the amount of data to transmit may be less (hence, more
energy efficient). The first communication link 1304 may operate
through the use of one of many wireless technologies such as
Bluetooth, Zigbee, WiFi, IrDA (infrared data association), wireless
USB, or Z-wave, to name a few. Alternatively, the communication
link 1304 may occur in the wireless medical band between 2360 MHz
and 2390 MHz, which the FCC allocated for medical body area network
devices, or in other designated medical device or WMTS bands. These
are examples of devices that can be used in the body area network
and surroundings, but other devices could also be used and are
included in the scope of this disclosure.
[0120] The personal device 1305 may store, process, display, and
transmit some of the data from the measurement device 1301. The
device 1305 may comprise a receiver, transmitter, display, voice
control and speakers, and one or more control buttons or knobs and
a touch screen. Examples of the device 1305 include smart phones
such as the Apple iPhones.RTM. or phones operating on the Android
or Microsoft systems. In one embodiment, the device 1305 may have
an application, software program, or firmware to receive and
process the data from the measurement device 1301. The device 1305
may then transmit some or all of the data or the processed data
over a second communication link 1306 to the internet or "cloud"
1307. The second communication link 1306 may advantageously
comprise at least one segment of a wireless transmission link,
which may operate using WiFi or the cellular network. The second
communication link 1306 may additionally comprise lengths of fiber
optic and/or communication over copper wires or cables.
[0121] The internet or cloud 1307 may add value to the measurement
device 1301 by providing services that augment the measured data
collected. In a particular embodiment, some of the functions
performed by the cloud include: (a) receive at least a fraction of
the data from the device 1305; (b) buffer or store the data
received; (c) process the data using software stored on the cloud;
(d) store the resulting processed data; and (e) transmit some or
all of the data either upon request or based on an alarm. As an
example, the data or processed data may be transmitted 1308 back to
the originator (e.g., patient or user), it may be transmitted 1309
to a health care provider or doctor or dentist, or it may be
transmitted 1310 to other designated recipients.
[0122] Service providers coupled to the cloud 1307 may provide a
number of value-add services. For example, the cloud application
may store and process the dental data for future reference or
during a visit with the dentist or healthcare provider. If a
patient has some sort of medical mishap or emergency, the physician
can obtain the history of the dental or physiological parameters
over a specified period of time. In another embodiment, alarms,
warnings or reminders may be delivered to the user 1308, the
healthcare provider 1309, or other designated recipients 1310.
These are just some of the features that may be offered, but many
others may be possible and are intended to be covered by this
disclosure. As an example, the device 1305 may also have a GPS
sensor, so the cloud 1307 may be able to provide time, date, and
position along with the dental or physiological parameters. Thus,
if there is a medical or dental emergency, the cloud 1307 could
provide the location of the patient to the dental or healthcare
provider 1309 or other designated recipients 1310. Moreover, the
digitized data in the cloud 1307 may help to move toward what is
often called "personalized medicine." Based on the dental or
physiological parameter data history, medication or medical/dental
therapies may be prescribed that are customized to the particular
patient. Another advantage for commercial entities may be that by
leveraging the advances in wireless connectivity and the widespread
use of handheld devices such as smart phones that can wirelessly
connect to the cloud, businesses can build a recurring cost
business model even using non-invasive measurement devices.
[0123] Described herein are just some examples of the beneficial
use of near-infrared or SWIR lasers for non-invasive measurements
of dental caries and early detection of carious regions. However,
many other dental or medical procedures can use the near-infrared
or SWIR light consistent with this disclosure and are intended to
be covered by the disclosure.
[0124] Although the present disclosure has been described in
several embodiments, a myriad of changes, variations, alterations,
transformations, and modifications may be suggested to one skilled
in the art, and it is intended that the present disclosure
encompass such changes, variations, alterations, transformations,
and modifications as falling within the spirit and scope of the
appended claims.
[0125] While exemplary embodiments are described above, it is not
intended that these embodiments describe all possible forms of the
disclosure. Rather, the words used in the specification are words
of description rather than limitation, and it is understood that
various changes may be made without departing from the spirit and
scope of the disclosure. Additionally, the features of various
implementing embodiments may be combined to form further
embodiments of the disclosure. While various embodiments may have
been described as providing advantages or being preferred over
other embodiments with respect to one or more desired
characteristics, as one skilled in the art is aware, one or more
characteristics may be compromised to achieve desired system
attributes, which depend on the specific application and
implementation. These attributes include, but are not limited to:
cost, strength, durability, life cycle cost, marketability,
appearance, packaging, size, serviceability, weight,
manufacturability, ease of assembly, etc. The embodiments described
herein that are described as less desirable than other embodiments
or prior art implementations with respect to one or more
characteristics are not outside the scope of the disclosure and may
be desirable for particular applications.
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