U.S. patent application number 13/330649 was filed with the patent office on 2012-04-19 for preparing samples for optical measurement.
Invention is credited to Masud AZIMI, Arran BIBBY, Christopher D. BROWN, Peili CHEN, Kevin J. KNOPP, Stephen MCLAUGHLIN, Daryoosh VAKHSHOORI, Peidong WANG.
Application Number | 20120092658 13/330649 |
Document ID | / |
Family ID | 41088553 |
Filed Date | 2012-04-19 |
United States Patent
Application |
20120092658 |
Kind Code |
A1 |
AZIMI; Masud ; et
al. |
April 19, 2012 |
PREPARING SAMPLES FOR OPTICAL MEASUREMENT
Abstract
We disclose an apparatus comprising: a hand-portable optical
analysis unit including an optical interface; and a device
configured to receive and releasably engage the hand-portable
optical analysis unit. The device comprises: a housing; a sample
unit in the housing; and a resilient member configured to bias the
sample unit and the hand-portable analysis unit towards each other
when the hand-portable optical analysis unit is received in the
device to compress a sample disposed between the sample unit and
the optical interface of the optical analysis unit. Methods of
analyzing samples are also disclosed.
Inventors: |
AZIMI; Masud; (Belmont,
MA) ; BIBBY; Arran; (Savannah, GA) ; BROWN;
Christopher D.; (Haverhill, MA) ; CHEN; Peili;
(Andover, MA) ; KNOPP; Kevin J.; (Newburyport,
MA) ; VAKHSHOORI; Daryoosh; (Cambridge, MA) ;
WANG; Peidong; (Carlisle, MA) ; MCLAUGHLIN;
Stephen; (Andover, MA) |
Family ID: |
41088553 |
Appl. No.: |
13/330649 |
Filed: |
December 19, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12414111 |
Mar 30, 2009 |
8081305 |
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13330649 |
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11864304 |
Sep 28, 2007 |
7675611 |
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12414111 |
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60931086 |
May 21, 2007 |
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Current U.S.
Class: |
356/244 |
Current CPC
Class: |
G01J 3/0202 20130101;
G01J 3/0256 20130101; G01J 3/4535 20130101; G01J 3/0272 20130101;
G01J 3/0286 20130101; G01J 3/0264 20130101; G01N 21/552 20130101;
G01J 3/024 20130101; G01J 3/0291 20130101; G01J 3/02 20130101 |
Class at
Publication: |
356/244 |
International
Class: |
G01N 21/01 20060101
G01N021/01 |
Claims
1. An apparatus comprising a hand-portable optical analysis unit
including an optical interface; and a device configured to receive
and releasably engage the hand-portable optical analysis unit, the
device comprising: a housing; a sample unit in the housing; and a
resilient member configured to bias the sample unit and the
hand-portable analysis unit towards each other to compress a sample
disposed between the sample unit and the optical interface of the
optical analysis unit when the hand-portable optical analysis unit
is received in the device.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 12/414,111 filed Mar. 30, 2009, which is a
continuation-in-part of U.S. patent application Ser. No.
11/864,304, filed on Sep. 28, 2007, which claims priority under 35
U.S.C. .sctn.119 to U.S. Provisional Application No. 60/931,086,
filed on May 21, 2007, the entire contents of which are
incorporated herein by reference in their entirety.
TECHNICAL FIELD
[0002] This disclosure relates to optical measurement and
identification of samples.
BACKGROUND
[0003] Optical measurement devices can be used by security
personnel to identify unknown substances that may potentially pose
a threat to public safety. For example, infrared radiation can be
used to interrogate and identify the unknown substances.
SUMMARY
[0004] In general, a sample preparation device can be configured to
compress a sample (e.g., a sample of solid material) between the
sample preparation device and a hand-portable optical analysis unit
including an optical interface. Applying pressure to the sample
during analysis can improve a signal-to-noise ratio in measurements
of a reflected radiation beam, and can enable measurement of
certain samples which would otherwise yield inconclusive
results.
[0005] In one aspect, an apparatus includes a hand-portable optical
analysis unit including an optical interface; and a device
configured to receive and releasably engage the hand-portable
optical analysis unit. The device includes: a housing; a sample
unit in the housing; and a resilient member configured to bias the
sample unit and the hand-portable analysis unit towards each other
to compress a sample disposed between the sample unit and the
optical interface of the optical analysis unit when the
hand-portable optical analysis unit is received in the device.
[0006] In one aspect, an apparatus includes: a device configured to
receive and releasably engage a handportable analysis unit. The
device includes: a housing; a sample unit movably disposed in the
housing; and a resilient member configured to bias the sample unit
towards the hand-portable analysis unit when the hand-portable
analysis unit is received in the device.
[0007] Embodiments of the apparatus can include one or more of the
following features.
[0008] In some embodiments, the sample unit includes a projection
extending outward from adjacent portions of the sample unit, the
projection aligned with the optical interface of the hand-portable
optical analysis unit when the hand-portable optical analysis unit
is received in the device. In some cases, the sample unit comprises
a concave surface from which the projection extends.
[0009] In some embodiments, the device is configured to apply a
pressure of between about 1,000 and about 3,000 pounds per square
inch to portions of a sample disposed between the projection of the
sample unit and the optical interface of the optical analysis unit
when the hand-portable optical analysis unit is received in the
device. In some cases, the sample unit is displaced between about
0.075 inches and about 0.105 inches from a rest position when the
hand-portable optical analysis unit is received in the device. In
some cases, the projection of the sample unit comprises a
substantially planar surface oriented towards the hand-portable
analysis unit when the hand-portable optical analysis unit is
received in the device. The substantially planar surface can have a
total area of between about 5.0 and about 7.0 square
millimeters.
[0010] In some embodiments, the projection of the sample unit
comprises a material with a hardness of at least 8 on the Mohs
scale.
[0011] In some embodiments, the projection of the sample unit
comprises sapphire, diamond, or ruby.
[0012] In some embodiments, the housing defines an internal
aperture and the sample unit is movably disposed in the internal
aperture. In some cases, the resilient member biases the sample
unit towards the hand-portable analysis unit when the hand-portable
optical analysis unit is received in the device. The resilient
member can be a spring with a spring rate between about 20 and
about 25 pounds per inch.
[0013] In some embodiments, the optical analysis unit weighs
between about 2.5 and about 3.5 pounds and the device weighs
between about 1 and about 2 pounds.
[0014] In some embodiments, wherein the optical interface is a
prism.
[0015] In some embodiments, the sample receptacle is open to the
atmosphere.
[0016] In some embodiments, the housing comprises retention members
configured to engage and hold the hand-portable analysis unit in
place against a force exerted by the resilient member. In some
cases, the sample unit includes a projection extending outward from
adjacent portions of the sample unit, the projection aligned with
an optical interface of a hand-portable optical analysis unit when
the hand-portable optical analysis unit is received in the
device.
[0017] In some embodiments, the housing comprises a substantially
flat surface opposite the sample unit.
[0018] In one aspect, an apparatus includes both an infrared
spectrometer and a Raman analyzer. The Raman analyzer includes a
lens focusing incident radiation on a sample being analyzed.
[0019] In some embodiments, the lens focusing incident radiation on
a sample being analyzed can be translated parallel to an optical
axis of the lens. In some cases, the lens can have a range of
motion that includes a first position in which the lens focuses an
incident radiation beam at point co-located with the exterior
surface of a prism of the infrared spectrometer. A portion of the
radiation can be scattered by the sample and the scattered
radiation (or a portion thereof) passes through the optical
assembly and redirected by an Raman optical assembly to enter a
radiation analyzer. The range of motion of the lens can also
include a second position in which the lens focuses incident
radiation beam at a point past the exterior surface of the prism.
In this position, the Raman subsystem can be used to analyze
samples that are spaced apart from optical analysis device.
[0020] The apparatus is configured so that, during operation, an
electronic processor determines information about a sample placed
in contact with the exposed surface of the prism based on radiation
reflected from the exposed prism surface while it is in contact
with the sample.
[0021] The information about the sample can include sample
information, and the electronic processor can be configured to
compare the sample information to reference information. The
electronic processor can be configured to retrieve the reference
information from a storage medium prior to comparing the sample and
reference information. The sample information and reference
information can include infrared absorption information.
[0022] The processor can be configured to apply a mathematical
transformation to the sample information prior to the comparing,
where the transformation transforms the sample information from a
first measurement domain to a second measurement domain. The
transformation can be a Fourier transformation.
[0023] The electronic processor can be configured to determine an
identity of the sample based on the comparison. Determining an
identity can include determining that the sample information
corresponds to reference information for a particular substance.
The processor can be configured to output a signal to an electronic
display based on the comparison. The signal can indicate to a human
operator that the sample information does not correspond to
reference information available to the electronic processor. The
signal can indicate to a human operator that the sample information
corresponds to reference information for a particular substance.
The signal can include a quantitative metric that corresponds to a
measurement of a correspondence between the sample information and
the reference information.
[0024] The electronic processor can be configured to make multiple
measurements of information about the sample, at least some of the
multiple measurements corresponding to different positions of the
second reflector. A maximum difference among the different
positions of the second reflector can be 2 mm or more (e.g., 5 mm
or more).
[0025] The electronic processor can be configured to obtain a first
identity of the sample that is determined based on Raman scattering
information about the sample, and to compare the first identity to
a second identity of the sample that is determined based on the
comparison between the sample and reference information. The first
identity can be obtained from a device configured to measure Raman
scattering information about the sample. The first identity can be
obtained over a communication link.
[0026] The electronic processor can be configured to obtain Raman
scattering information about the sample, and to compare the sample
Raman scattering information to reference Raman scattering
information. The electronic processor can be configured to retrieve
the reference Raman scattering information from a storage medium
prior to comparing the sample Raman scattering information and the
reference Raman scattering information. The electronic processor
can be configured to determine an identity of the sample based on
the comparison between the sample and reference information, and
based on the comparison between the sample and reference Raman
scattering information. The Raman scattering information about the
sample can be obtained from another device over a communication
link.
[0027] The radiation source can be a first radiation source and the
radiation detector can be a first radiation detector, and the
apparatus can include a second radiation source configured to
direct radiation to be incident on the sample, and a second
radiation detector configured to detect radiation scattered from
the sample. The radiation provided by the second radiation source
can pass through the exposed surface of the prism prior to being
incident on the sample.
[0028] The radiation provided by the second radiation source can
include a distribution of radiation wavelengths, where a center
wavelength of the distribution is 400 nm or less (e.g., 350 nm or
less). An intensity of the radiation provided by the second
radiation source can be 5 mW or less (e.g., 2 mW or less).
[0029] The second radiation source can include a laser diode.
[0030] The second detector can include a detector configured to
measure radiation intensity at a plurality of different
wavelengths. The second detector can include a Raman
spectrometer.
[0031] The sample can include a solid (e.g,. a powder).
Alternatively, or in addition, the sample can include a liquid
and/or a gel. The sample can include a mixture of two or more
substances.
[0032] Embodiments of the apparatus can also include any of the
other features disclosed herein.
[0033] In one aspect, a method of analyzing a sample includes:
placing the sample in a sample receptacle of a device; pressing a
hand-portable optical analysis unit into locking engagement with
the device such that the sample is disposed between the sample
receptacle and an optical interface of the optical analysis unit;
compressing the sample between a sample interface of the sample
receptacle and an optical interface of the optical analysis unit;
directing radiation from the optical analysis unit towards the
sample; determining information about the sample by detecting
radiation; and removing the hand-portable optical analysis unit
from the device.
[0034] Embodiments of the method can include one or more of the
following features.
[0035] In some embodiments, compressing the sample comprises
displacing the sample receptacle from a rest position of the sample
receptacle. In some cases, compressing the sample comprises
applying a force to the sample receptacle that is proportional to a
distance that the sample receptacle is displaced from the rest
position.
[0036] In some embodiments, compressing the sample comprises
automatically controlling force applied to the sample by the device
and the optical analysis unit.
[0037] In some embodiments, compressing the sample comprises
displacing a portion of the sample from between the sample
interface of the sample receptacle and the optical interface of the
optical analysis unit.
[0038] In some embodiments, determining information about the
sample comprises measuring infrared absorption information about
the sample. Determining information about the sample can include
measuring infrared absorption information about the sample. In some
cases, determining information about the sample comprises obtaining
Raman scattering information about the sample. Methods can also
include determining an identity of the sample based on sample
information (e.g., the infrared absorption information and the
Raman scattering information about the sample). Determining an
identity can include comparing the sample information to reference
information stored in a storage unit.
[0039] Obtaining Raman scattering information can include receiving
Raman scattering information from a device over a communication
link. Alternatively, or in addition, obtaining Raman scattering
information can include measuring electromagnetic radiation
scattered by the sample. The exposed surface of the prism can form
a first aperture, and measuring electromagnetic radiation scattered
by the sample can include measuring radiation received in a second
aperture different from the first aperture. The electromagnetic
radiation scattered by the sample can enter the prism through the
exposed surface and can be detected after it leaves the prism.
[0040] Embodiments of the method can also include any of the other
method steps disclosed herein, as appropriate.
[0041] Embodiments can include one or more of the following
advantages.
[0042] Applying pressure to the sample during analysis can improve
a signal-to-noise ratio in measurements of a reflected radiation
beam, and can enable measurement of certain samples which would
otherwise yield inconclusive results. The sample preparation
devices described herein can automatically provide a specific level
of pressure to a solid sample during analysis. Small and
self-contained sample preparation devices are easy to use and do
not require fine adjustments making them particularly useful for
field operations including, for example, identification of samples
by personnel in Hazmat suits and/or other protective gear.
[0043] Use of a projection with a small contact area allows a
relatively small force to provide a relatively high pressure on the
sample being analyzed. This can enable a user to relatively easily
insert the measuring device into place in the sample preparation
device.
[0044] A measuring device with a Raman optical assembly with a
movable focusing lens can be used in at least two modes. The
measuring device be used in a first mode (e.g., with the focusing
lens in a position in which the lens focuses an incident radiation
beam at point co-located with the exterior surface of a prism of
the infrared spectrometer) to identify samples in contact with an
optical interface of the measuring device, in this mode, the
measuring device can use both infrared spectrometry and Raman
analysis to provide dual mode analysis of samples such as powders
that the measuring device can be pressed against. The measuring
device can also be used in a second mode (e.g., with the focusing
lens in a position in which the lens focuses incident radiation
beam at a point past the exterior surface of the prism) to use
Raman analysis to identify samples that are spaced apart from
optical analysis device (e.g., the contents of a bottle at an
airport checkpoint).
[0045] The measurement devices disclosed herein include handheld
Fourier transform infrared (FTIR) scanners that are robust and
relatively simple to operate, so that operators with relatively
limited training are capable of successfully using the devices. For
example, embodiments of the measurement devices can include rugged
housings which can prevent damage to internal components from rough
handling, and/or a user interface which provides simple indicators
that do not require specialized knowledge to interpret. Further,
the devices can be automatically configured to alert additional
(e.g., more highly-trained) personnel if hazardous substances are
detected.
[0046] Measurement devices can be reliably and repeatably used in a
variety of environments, including uncontrolled environments. For
example, the measurement devices can be constructed in a way that
facilitates ease of use and maintenance in uncontrolled
environments. As an example, measurement devices can include a
prism used to contact samples, and the prism can be sealed within a
protrusion of the device's enclosure. The position of the prism
relative to the enclosure permits the prism to be placed in contact
with a sample during operation, and can allow a system operator to
apply pressure to the sample. After completing a measurement of the
sample, the position of the prism facilitates cleaning prior to
testing of another sample. The seal prevents penetration of the
sample into the enclosure, even when the sample is a fluid or
gel.
[0047] Certain embodiment include moving mirrors. These mirrors can
have high reflectivities for both sample measurement beams and
position measurement beams, so that both sample information and
mirror position information can be measured accurately and with
high sensitivity. For example, a movable mirror within the
measurement device can include a first reflecting surface from
which a sample measurement beam reflects, and a second reflecting
surface opposite the first reflecting surface from which a
position-measuring beam reflects. By directing the
position-measuring beam to reflect from a surface opposite the
first surface, a reflective material or coating applied to the
first reflecting surface can be chosen for a wavelength of the
sample measurement beam, and a reflective material or coating
applied to the second reflecting surface can be chosen for a
wavelength of the position-measuring beam, which is different from
the wavelength of the sample measurement beam. Movable mirrors can
be connected to a translation mechanism that provides for a
relatively large range of motion of the mirror, and which prevents
vibrational disturbances from perturbing the optical components of
the measurement device. For example, the movable mirror can be
connected to a shaft, and the shaft can be positioned within a
bushing such that the shaft is movable relative to the bushing. A
fluid can be positioned between the shaft and bushing to provide
for smooth movement between shaft and bushing. The combination of
the shaft and bushing permit movement of the mirror, and the shaft
and bushing provide a significantly larger range of mirror movement
than the range of movement permitted by leaf springs and similar
devices. Further, the fluid decouples the shaft and bushing, so
that mechanical disturbances (e.g., vibrations) are not coupled
between the mirror and the rest of the optical assembly.
[0048] The measurement devices disclosed herein can also be
relatively tolerant to a variety of environments, and to rough
handling during deployment. For example, a vibration-damping
material can be positioned between an inner wall of the enclosure
and the optical assembly. The vibration-damping material dissipates
mechanical disturbances that arise, for example, from handling of
the enclosure by a system operator. The amplitude of such
disturbances can be significantly reduced or eliminated by the
vibration-damping material, so that the alignment of optical
components within the enclosure is not disturbed.
[0049] The measurement devices can be configured to identify
samples with a relatively high degree of certainty. For example,
the measurement devices disclosed herein can be configured to
identify samples based on both infrared absorption information and
Raman scattering information. For certain samples, one type of
information (e.g., Raman scattering information) can be used to
confirm an identity of the sample that is determined using the
other type of information (e.g., infrared absorption information).
In this way, identification of samples can be performed with a
higher degree of certainty than would generally be possible based
on only one type of information. For some samples, Raman scattering
information may provide relatively poor diagnostic information, and
infrared absorption information can primarily be used to identify
the sample. Conversely, for some samples, infrared absorption
information may provide relatively poor diagnostic information, and
Raman scattering information can primarily be used to identify the
sample. In this manner, the infrared absorption information and
Raman scattering information can be complementary to one another.
The measurement devices can be configured to automatically
determine whether to use only infrared absorption information, only
Raman scattering information, or both types of information.
[0050] Unless otherwise defined, all technical and scientific terms
used herein have the same meaning as commonly understood by one of
ordinary skill in the art. Although methods and materials similar
or equivalent to those described herein can be used in the practice
or testing of the disclosure, suitable methods and materials are
described below. All publications, patent applications, patents,
and other references mentioned herein are incorporated by reference
in their entirety. In case of conflict, the present specification,
including definitions, will control. In addition, the materials,
methods, and examples are illustrative only and not intended to be
limiting.
[0051] The details of one or more embodiments are set forth in the
accompanying drawings and the description below. Other features and
advantages will be apparent from the description, drawings, and
claims.
DESCRIPTION OF DRAWINGS
[0052] FIG. 1 is a schematic diagram of an embodiment of a
measurement device.
[0053] FIG. 2 is a schematic diagram of an embodiment of an
interferometer mirror.
[0054] FIG. 3 is a schematic diagram of an embodiment of an
aperture.
[0055] FIG. 4 is a plan view of an embodiment of an aperture.
[0056] FIG. 5 is a cross-sectional view of an embodiment of a
measurement device.
[0057] FIG. 6 is a schematic diagram of an embodiment of an
enclosure.
[0058] FIG. 7 is a schematic diagram of an embodiment of a portable
support structure.
[0059] FIG. 8 is a schematic diagram of an embodiment of a
measurement device that includes an infrared spectrometer and a
Raman spectrometer.
[0060] FIGS. 9A and 9B are plots of infrared absorption information
and Raman scattering information for a sample of 3% hydrogen
peroxide in water.
[0061] FIGS. 10A and 10B are plots of infrared absorption
information and Raman scattering information for a sample of
isopropanol.
[0062] FIGS. 11A and 11B are plots of infrared absorption
information and Raman scattering information for a sample of a
pesticide.
[0063] FIG. 12 is a schematic diagram of an embodiment of a
measurement device that includes an infrared spectrometer and a
Raman spectrometer.
[0064] FIGS. 13A and 13B are schematic views of a portion of an
embodiment of a measurement device that includes an infrared
spectrometer and a Raman spectrometer.
[0065] FIG. 14A is a perspective view of a sample preparation
device and a measurement device.
[0066] FIGS. 14B and 14C are views of a portion of the sample
preparation device (cross-sectional) and the measurement device
(side view) shown in FIG. 14A at different scales.
[0067] FIG. 15 is a perspective view of the sample preparation
device of FIG. 14A.
[0068] FIG. 16 is a perspective view of the measuring device of
FIG. 14A.
[0069] Like reference symbols in the various drawings indicate like
elements.
DETAILED DESCRIPTION
[0070] Many applications exist for portable measurement devices,
including field identification of unknown substances by law
enforcement and security personnel, detection of prohibited
substances at airports and in other secure and/or public locations,
and identification pharmaceutical agents, industrial chemicals,
explosives, energetic materials, and other agents. To be useful in
a variety of situations, it can be advantageous for portable
measurement devices to have a handheld form factor and to rapidly
provide accurate results.
[0071] In certain embodiments, the measurement devices and methods
disclosed herein provide for contact between a sample of interest
and the measurement device via a prism positioned in a protrusion
of the measurement device's enclosure. The prism, which can be
formed from a relatively hard material such as diamond, operates by
ensuring that non-absorbed incident radiation is directed to a
detector after undergoing total internal reflection within the
prism. As a result, reflected radiation is coupled with high
efficiency to the detector, ensuring sensitive operation of the
measurement devices.
[0072] Samples of interest can be identified based on the reflected
radiation that is measured by the detector. The reflected radiation
can be used to derive infrared absorption information corresponding
to the sample, and the sample can be identified by comparing the
infrared absorption information to reference information for the
sample that is stored in the measurement device. In addition to the
identity of the sample, the measurement device can provide one or
more metrics (e.g., numerical results) that indicate how closely
the infrared absorption information matches the reference
information. Further, the measurement device can compare the
identity of the sample of interest to a list of prohibited
substances--also stored within the measurement device--to determine
whether particular precautions should be taken in handling the
substance, and whether additional actions by security personnel,
for example, are warranted. A wide variety of different samples can
be interrogated, including solids, liquids, gels, powders, and
various mixtures of two or more substances.
[0073] FIG. 1 shows a schematic diagram of a measurement device
100. Device 100 includes an optical assembly mounted on an assembly
support 152 that is fixed within an enclosure 156. The optical
assembly includes: radiation sources 102 and 144; mirrors 104, 108,
110, 148, 118, 120, 126, 128, and 130; beamsplitters 106 and 146;
detectors 132 and 150; and prism 122. Device 100 also includes a
shaft 112, a bushing 114, and an actuator 116 coupled to mirror
110, and an electronic processor 134, an electronic display 136
(e.g., including a flat panel display element such as a liquid
crystal display element, an organic light-emitting diode display
element, an electrophoretic display element, or another type of
display element), an input device 138, a storage unit 140, and a
communication interface 142. Electronic processor 134 is in
electrical communication with detector 132, storage unit 140,
communication interface 142, display 136, input device 138,
radiation sources 102 and 144, detector 150, and actuator 116,
respectively, via communication lines 162a-i.
[0074] Measurement device 100 is configured for use as a Fourier
transform infrared (FTIR) spectrometer. During operation, radiation
168 is generated by radiation source 102 under the control of
processor 134. Radiation 168 is directed by mirror 104 to be
incident on beamsplitter 106, which is formed from a beamsplitting
optical element 106a and a phase compensating plate 106b, and which
divides radiation 168 into two beams. A first beam 170 reflects
from a surface of beamsplitter 106, propagates along a beam path
which is parallel to arrow 171, and is incident on fixed mirror
108. Fixed mirror 108 reflects first beam 170 so that first beam
170 propagates along the same beam path, but in an opposite
direction (e.g., towards beamsplitter 106).
[0075] A second beam 172 is transmitted through beamsplitter 106
and propagates along a beam path which is parallel to arrow 173.
Second beam 172 is incident on a first surface 110a of movable
mirror 110. Movable mirror 110 reflects second beam 172 so that
beam 172 propagates along the same beam path, but in an opposite
direction (e.g., towards beamsplitter 106).
[0076] First and second beams 170 and 172 are combined by
beamsplitter 106, which spatially overlaps the beams to form
incident radiation beam 174. Mirrors 118 and 120 direct incident
radiation beam 174 to enter prism 122 through prism surface 122b.
Once inside prism 122, radiation beam 174 is incident on surface
122a of the prism 122. Surface 122a of prism 122 is positioned such
that it contacts a sample of interest 190. When radiation beam 174
is incident on surface 122a, a portion of the radiation is coupled
into sample 190 through surface 122a. Typically, for example,
sample 190 absorbs a portion of the radiation in radiation beam
174.
[0077] Radiation beam 174 undergoes total internal reflection from
surface 122a of prism 122 as reflected beam 176. Reflected beam 176
includes, for example, the portion of incident radiation beam 174
that is not absorbed by sample 190. Reflected beam 176 leaves prism
122 through surface 122c, and is directed by mirrors 126, 128, and
130 to be incident on detector 132. Under the control of processor
134, detector 132 measures one or more properties of the reflected
radiation in reflected beam 176. For example, detector 132 can
determine absorption information about sample 190 based on
measurements of reflected beam 176.
[0078] Typically, the radiation in reflected beam 176 is measured
at a plurality of positions of movable mirror 110. Mirrors 108 and
110, together with beamsplitter 106, are arranged to form a
Michelson interferometer, and by translating mirror 110 in a
direction parallel to arrow 164 prior each measurement of reflected
radiation 176, the plurality of measurements of the radiation in
reflected beam 176 form an interferogram. The interferogram
includes information such as sample absorption information.
Processor 134 can be configured to apply one or more mathematical
transformations to the interferogram to obtain the sample
absorption information. For example, processor 134 can be
configured to transform the interferogram measurements from a first
domain (such as time or a spatial dimension) to a second domain
(such as frequency) that is conjugate to the first domain. The
transform(s) that is/are applied to the data can include a Fourier
transform, for example.
[0079] Movable mirror 110 is coupled to shaft 112, bushing 114, and
actuator 116. Shaft 112 moves freely within bushing 114, and a
viscous fluid is disposed between shaft 112 and bushing 114 to
permit relative motion between the two. Mirror 110 moves when
actuator 116 receives control signals from processor 134 via
communication line 162i. Actuator 116 initiates movement of shaft
112 in a direction parallel to arrow 164, and mirror 110 moves in
concert with shaft 112. Bushing 114 provides support for shaft 112,
preventing wobble of shaft 112 during translation. However, bushing
114 and shaft 112 are effectively mechanically decoupled from one
another by the fluid disposed between them; mechanical disturbances
such as vibrations are coupled poorly between shaft 112 and bushing
114. As a result, the alignment of the Michelson interferometer
remains relatively undisturbed even when mechanical perturbations
such as vibrations are present in other portions of device 100.
[0080] To measure the position of mirror 110, device 100 includes a
second interferometer assembly that includes radiation source 144,
beamsplitter 146, mirror 148, and detector 150. These components
are arranged to form a Michelson interferometer. During a mirror
position measurement operation, radiation source 144 receives a
control signal from processor 134 via communication line 162g, and
generates a radiation beam 178. Beam 178 is incident on
beamsplitter 146, which separates radiation beam 178 into a first
beam 180 and a second beam 182. First beam 180 reflects from the
surface of beamsplitter 146 and is incident on a second surface
110b of mirror 110. Second surface 110b is positioned opposite
first surface 110a of mirror 110. First beam 180 reflects from
surface 110b and returns to beamsplitter 146.
[0081] Second beam 182 is transmitted through beamsplitter 146,
reflected by mirror 148, and returned to beamsplitter 146.
Beamsplitter 146 combines (e.g., spatially overlaps) reflected
beams 180 and 182, and the combined beam 184 is directed to
detector 150. Detector 150 receives control signals from processor
134 via communication line 162h, and is configured to measure an
intensity of combined beam 184. As the position of mirror 110
changes (e.g., due to translation of mirror 110 along a direction
parallel to arrow 164), the intensity of the radiation measured by
detector 150 changes due to interference between first beam 180 and
second beam 182 in combined beam 184. By analyzing the changes in
measured radiation intensity from detector 150, processor 134 can
determine with high accuracy the position of mirror 110.
[0082] Position information for mirror 110 is combined by processor
134 with measurements of the radiation in reflected beam 176 to
construct an interferogram for sample 190. As discussed above,
processor 134 can be configured to apply a Fourier transform to the
interferogram to obtain absorption information about sample 190
from the interferogram. The absorption information can be compared
by processor 134 to reference information (e.g., reference
absorption information) stored in storage unit 140 to determine an
identity of sample 190. For example, processor 134 can determine
whether the absorption information for the sample matches any one
or more of a plurality of sets of reference absorption information
for a variety of substances that are stored as database records in
storage unit 140. If a match is found (e.g., the sample absorption
information and the reference information for a particular
substance agree sufficiently), then sample 190 is considered to be
identified by processor 134. Processor 134 can send an electronic
signal to display 136 along communication line 162d that indicates
to a system operator that identification of sample 190 was
successful, and provides the name of the identified substance. The
signal can also indicate to the system operator how closely the
sample absorption information and the reference information agree.
For example, numeric values of one or more metrics can be provided
which indicate the extent of correspondence between the sample
absorption information and the reference information on a numerical
scale.
[0083] If a match between the sample absorption information and the
reference information is not found by processor 134, the processor
can send an electronic signal to display 136 that indicates to the
system operator that sample 190 was not successfully identified.
The electronic signal can include, in some embodiments, a prompt to
the system operator to repeat the sample absorption
measurements.
[0084] Reference information stored in storage unit 140 can include
reference absorption information for a variety of different
substances, as discussed above. The reference information can also
include one or more lists of prohibited substances. Lists of
prohibited substances can include, for example, substances that
passengers on commercial airline flights are not allowed to carry.
Lists of prohibited substances can also include, for example,
substances that are not permitted in various public locations such
as government buildings for security and public safety reasons. If
identification of sample 190 is successful, processor 134 can be
configured to compare the identity of sample 190 against one or
more lists of prohibited substances stored in storage unit 140. If
sample 190 appears on a list as a prohibited substance, processor
134 can alert the system operator that a prohibited substance has
been detected. The alert can include a warning message displayed on
display 136 and/or a colored region (e.g., a red-colored region) on
display 136. Processor 134 can also be configured to sound an audio
alarm via a speaker to alert the system operator.
[0085] Storage unit 140 typically includes a re-writable persistent
flash memory module. The memory module, which is removable from
enclosure 156, is configured to store a database that includes a
library of infrared absorption information about various
substances. Processor 134 can retrieve reference absorption
information from storage unit 140 via a request transmitted on
communication line 162b. Storage unit 140 can also store device
settings and other configuration information such as default
operating parameters. Other storage media can also be included in
storage unit 140, including various types of re-writable and
non-rewritable magnetic media, optical media, and electronic
memory.
[0086] Measurement device 100 also includes communication interface
142, which receives and transmits signals from/to processor 134 via
communication line 162c. Communication interface 142 includes a
wireless transmitter/receiver unit that is configured to transmit
signals from processor 134 to other devices, and to receive signals
from other devices and communicate the received signals to
processor 134. Typically, for example, communication interface 142
permits processor 134 to communicate with other devices--including
other measurement devices 100 and/or computer systems--via a
wireless network that includes multiple devices connected to the
network, and/or via a direct connection to another device.
Processor 134 can establish a secure connection (e.g., an encrypted
connection) to one or more devices to ensure that signals can only
be transmitted and received by devices that are approved for use on
the network.
[0087] Processor 134 communicates with a central computer system to
update the database of reference information stored in storage unit
140. Processor 134 is configured to periodically contact the
central computer system to receive updated reference information,
and processor 134 can also receive automatic updates that are
delivered by the central computer system. The updated reference
information can include reference absorption information, for
example, and can also include one or more new or updated lists of
prohibited substances.
[0088] Processor, 134 can also communicate with other measurement
devices to broadcast alert messages when certain substances--such
as substances that appear on a list of prohibited substances--are
identified, for example. Alert messages can also be broadcast to
one or more central computer systems. Alert information--including
the identity of the substance, the location at which the substance
was identified, the quantity of the substance, and other
information--can also be recorded and broadcast to other
measurement devices and computer systems.
[0089] In some embodiments, measurement device 100 can be connected
to other devices over other types of networks, including isolated
local area networks and/or cellular telephone networks. The
connection can be a wireless connection or a wired connection.
Signals, including alert messages, can be transmitted from
processor 134 to a variety of devices such as cellular telephones
and other network-enabled devices that can alert personnel in the
event that particular substances (e.g., prohibited substances) are
detected by measurement device 100.
[0090] Typically, input device 138 includes a control panel that
enables a system operator to set configuration options and change
operating parameters of measurement device 100. In some
embodiments, measurement device 100 can also include an
internet-based configuration interface that enables remote
adjustment of configuration options and operating parameters. The
interface can be accessible via a web browser, for example, over a
secured or insecure network connection. The internet-based
configuration interface permits remote updating of measurement
device 100 by a central computer system or another device, ensuring
that all measurement devices that are operated in a particular
location or for a particular purpose have similar configurations.
The internet-based interface can also enable reporting of device
configurations to a central computer system, for example, and can
enable tracking of the location of one or more measurement
devices.
[0091] Radiation source 102 includes one or more laser diodes
configured to provide infrared radiation, so that measurement
device 100 functions as an infrared spectrometer. Typically, for
example, the infrared radiation provided by source 102 includes a
distribution of wavelengths, and a center wavelength of the
distribution is about 785 nm. In general, radiation source 102 can
include a variety of sources, including--in addition to laser
diodes--light-emitting diodes and lasers. A center wavelength of
the distribution of wavelengths of the radiation provided by source
102 can be 700 nm or more (e.g., 750 nm or more, 800 nm or more,
850 nm or more, 900 nm or more, 950 nm or more, 1000 nm or more,
1050 nm or more, 1100 nm or more, 1150 nm or more, 1200 nm or more,
1300 nm or more, 1400 nm or more).
[0092] Typically, an intensity of radiation 168 provided by source
102 is about 50 mW/mm.sup.2. In general, however, the intensity of
radiation 168 can be varied (e.g., via a control signal from
processor 134 transmitted along communication line 162f) according
to the particular sample 190 and the sensitivity of detector 132.
In some embodiments, for example, the intensity of radiation 168
provided by source 102 is 10 mW/mm.sup.2 or more (e.g., 25
mW/mm.sup.2 or more, 50 mW/mm.sup.2 or more, 100 mW/mm.sup.2 or
more, 150 mW/mm.sup.2 or more, 200 mW/mm.sup.2 or more, 250
mW/mm.sup.2 or more, 300 mW/mm.sup.2 or more, 400 mW/mm.sup.2 or
more).
[0093] In certain embodiments, the properties of radiation 168
provides by source 102 can be altered by control signals from
processor 134. For example, processor 134 can adjust an intensity
and/or a spectral distribution of radiation 168. Processor 134 can
adjust spectral properties of radiation 168 by activating one or
more filter elements (not shown in FIG. 1), for example. In
general, measurement device 100 can include lenses, mirrors,
beamsplitters, filters, and other optical elements that can be used
to condition and adjust properties of radiation 168.
[0094] Detector 132 is configured to measure reflected radiation
beam 176 after the beam leaves prism 122. Typically, detector 132
includes a pyroelectric detector element that generates an
electronic signal, the magnitude of the signal being dependent on
an intensity of radiation beam 176. In general, however, detector
132 can include a variety of other detection elements. For example,
in some embodiments, detector 132 can be a photoelectric detector
(e.g., a photodiode) that generates an electronic signal with a
magnitude that depends on the intensity of radiation beam 176.
[0095] Radiation source 144 generates radiation beam 178 that is
used to measure the position of mirror 110. Radiation source 144
includes a vertical cavity surface-emitting laser (VCSEL) that
generates radiation having a central wavelength of 850 nm. In
general, radiation source 144 can include a variety of sources,
including laser diodes, light-emitting diodes, and lasers.
Radiation beam 178 can have a central wavelength in an ultraviolet
region, a visible region, or an infrared region of the
electromagnetic spectrum. For example, in some embodiments, a
central wavelength of radiation beam 178 is between 400 nm and 1200
nm (e.g., between 400 nm and 500 nm, between 500 nm and 600 nm,
between 600 nm and 700 nm, between 700 nm and 800 nm, between 800
nm and 900 nm, between 900 nm and 1000 nm, between 1000 nm and 1100
nm, between 1100 nm and 1200 nm).
[0096] Detector 150 can include a variety of different detection
elements configured to generate an electronic signal in response to
beam 184. In some embodiments, for example, detector 184 includes a
pyroelectric detector. In certain embodiments, detector 184
includes a photoelectric detector, such as a photodiode. Generally,
any detection element that generates an electronic signal that is
sensitive to changes in an intensity of beam 184 can be used in
detector 150.
[0097] As shown in FIG. 1, mirror 110 includes two opposite
reflecting surfaces 110a and 110b. An enlarged schematic diagram of
mirror 110 is shown in FIG. 2. Mirror 110 includes a substrate 110c
(formed of glass or fused silica, for example), with a first
coating 110d disposed on substrate 110c to form first reflecting
surface 110a, and a second coating 110e disposed on an opposite
surface of substrate 110c to form second reflecting surface 110e.
Typically, beams 172 and 180, which are incident on surfaces 110a
and 110b of mirror 110, respectively, have different central
wavelengths. The materials that form first coating 110d and second
coating 110e are selected to provide high reflectivity for beams
172 and 180. In some embodiments, depending on the central
wavelengths of beams 172 and 180, a single coating material with
high reflectivity at both central wavelengths is used to form
coatings 110d and 110e. In certain embodiments, two different
materials are used to form coatings 110d and 110e, where each
coating material is selected to provide high reflectivity of beam
172 or beam 180, as appropriate.
[0098] The use of two different coating materials--each selected to
provide high reflectivity for a beam having a particular central
wavelength--provides an advantage over conventional
position-measuring interferometer systems. In certain conventional
systems, for example, beams 172 and 180 reflect from a common
surface of mirror 110 (e.g., surface 110a). If beams 172 and 180
have central wavelengths that differ appreciably, then it is
difficult to find a material for coating 110d that has very high
reflectivity for both beams. As a result, one or even both of beams
172 and 180 is reduced in intensity due to reflection losses from
mirror 110.
[0099] Shaft 112 and bushing 114 permit smooth, vibration-decoupled
motion of mirror 110 in a direction parallel to arrow 164 (e.g., in
a direction parallel to the optical path of beam 172). In the
embodiment shown in FIG. 1, both shaft 112 and bushing 114 are
substantially cylindrical, and bushing 114 has a central bore
adapted to receive shaft 112. In general, however, shaft 112 can be
replaced by any member that is connected to mirror so that the
member moves together with mirror 110. Similarly, bushing 114 can,
in general, include any sleeve or other member that is adapted to
receive shaft 112, and configured to permit motion of shaft 112 and
mirror 110 relative to bushing 114.
[0100] Shaft 112 and bushing 114 can generally be formed from the
same material, or from different materials. Typically, shaft 112
and bushing 114 are formed from hard, smooth materials. Exemplary
materials that can be used to form shaft 112 and/or bushing 114
include, but are not limited to, zirconia, aluminum oxide, silicon
carbide, steel, and/or glass.
[0101] As discussed above, a fluid is disposed between shaft 112
and bushing 114. Typically, the fluid is a viscous fluid that
permits relatively friction-free movement of shaft 112 relative to
bushing 114. The fluid also decouples shaft 112 and bushing 114, so
that mechanical disturbances in one of these elements (e.g.,
bushing 114) are not effectively transmitted to the other element
(e.g., shaft 112). The fluid therefore ensures that many of the
optical elements--and mirror 110 in particular--of measurement
device 100 are not significantly disturbed by mechanical
perturbations. A variety of different fluids can be used between
shaft 112 and bushing 114 including, for example, silicone oil.
[0102] The overall translation mechanism that is configured to
translate mirror 110 includes shaft 112, bushing 114, and actuator
116. Actuator 116 is coupled to shaft 112 and, on receiving
suitable control signals from processor 134, translates mirror 110
in a direction parallel to the optical path of beam 172 by applying
a force to shaft 112. Due to the applied force, shaft 112 moves
relative to bushing 114, causing translation of mirror 110.
Typically, actuator 116 includes a coil winding that is configured
to generate a magnetic field when a control signal is received. The
magnetic field produces an attractive or repulsive force between
actuator 116 and bushing 114 (which can be formed from a metal
and/or magnetic material, for example), causing translational
motion of actuator 116 and coupled shaft 112 relative to bushing
114. In general, many different types of actuators can be used to
translate mirror 110. Exemplary alternative actuators include voice
coil actuators, stepper motors, flexure-based translation stages,
and piezoelectric devices.
[0103] Measurement device 100 is generally configured to make
multiple measurements of infrared absorption information from
sample 190 to construct an interferogram. Typically, for example,
each of the multiple measurements corresponds to a different
position of mirror 110 along an axis parallel to the beam path of
beam 172. In certain embodiments, a maximum difference among the
different positions of mirror 110 is 0.5 mm or more (e.g., 1 mm or
more, 2 mm or more, 3 mm or more, 4 mm or more, 5 mm or more, 7 mm
or more, 10 mm or more).
[0104] As discussed above, during operation, prism 122 is placed in
contact with sample 190. Radiation is incident on surface 122a of
prism 122 that contacts sample 190, and a portion of the incident
radiation couples into sample 190 where it is absorbed. The
remaining radiation undergoes total internal reflection from
surface 122a of prism 122, and is detected by a suitable detector
132. To contact sample 190, prism 122 is positioned in an aperture
than includes a protrusion 166 formed in a wall of enclosure 156.
Typically, protrusion 166 includes a liquid-proof seal to prevent
sample fluid from entering enclosure 156 when prism 122 contacts a
liquid sample 190.
[0105] FIG. 3 shows an enlarged schematic view of the aperture
including protrusion 166. Prism 122 includes a surface 122a that is
positioned to contact sample 190. Radiation enters prism 122
through surface 122b, and leaves prism 122 through surface 122c.
Surface 122a includes a coating 206.
[0106] An edge of prism 122 opposite to surface 122a is supported
from below by a prism base 204. Surface 122a of prism 122 is also
attached to mounting plate 202 to provide support to prism 122 from
above. Support provided by plate 202 and base 204 allows prism 122
to withstand significant applied forces during operation without
being displaced from its mounting position within protrusion 166.
During operation, a system operator can position measurement device
100 so that prism 122 (e.g., surface 122a) contacts sample 190, and
the operator can apply a force to enclosure 156 so that prism 122
exerts a compressive force on sample 190. This can improve a
signal-to-noise ratio in measurements of reflected radiation beam
176, and can enable measurement of certain samples which would
otherwise yield inconclusive results in the absence of direct
contact with prism 122 and/or the application of compressive force
to sample 190. Support base 204 and mounting plate 202 ensure that
prism 122 remains in the same position within protrusion 166 during
application of these forces.
[0107] Mounting plate 202 and support base 204 can be formed from
the same or different materials. Typically, for example, mounting
plate 202 and support base 204 include one or more metals.
Exemplary materials from which either or both of mounting plate 202
and support base 204 can be formed include stainless steel and
Hastelloy.
[0108] As discussed above, surface 122a of prism 122 includes a
coating 206. Coating 206 can include one or more metals such as,
for example, gold. A metal coating 206 permits attachment of
surface 122a to mounting plate 202 via soldering, welding, or
brazing. In FIG. 3, prism 122 is soldered to mounting plate 202 via
solder joints 208 between mounting plate 202 and coating 206.
[0109] To withstand physical handling during measurement and
chemical attack by samples, prism 122 is typically formed from a
hard, chemically inert material. Prism 122 is also configured to
provide for total internal reflection of radiation beam 174, and so
prism 122 is typically formed from a relatively high refractive
index material. Materials that can be used to form prism 122
include naturally occurring and synthetic diamond, for example.
[0110] Protrusion 166 extends outward for a distance e from
enclosure 156. The extension of protrusion 166 permits contact
between sample 190 and surface 122a of prism 122, and at the same
time prevents contact between sample 190 and the rest of
measurement device 100. In general, the distance e can be selected
according to the type and environment of the samples of interest.
In some embodiments, for example, e can be 10 mm or more (e.g., 20
mm or more, 30 mm or more, 40 mm or more) and/or 100 mm or less
(e.g., 90 mm or less, 80 mm or less, 70 mm or less, 60 mm or
less).
[0111] FIG. 4 shows a plan view of the aperture that includes
protrusion 166. In the embodiment shown, surface 122a of prism 122
has a substantially circular cross-sectional shape. In general,
however, prism 122 can have a variety of different cross-sectional
shapes, including ellipsoidal, rectangular, triangular, square, and
irregular.
[0112] Surface 122a of prism 122, which is substantially planar in
the embodiment shown in FIG. 4, has a maximum dimension f. In
certain embodiments, f can be 10 mm or less (e.g., 9 mm or less, 8
mm or less, 7 mm or less, 6 mm or less, 5 mm or less, 4 mm or less,
3 mm or less, 2 mm or less, 1 mm or less, 0.5 mm or less). In some
embodiments, an area of surface 122a can be 500 mm.sup.2 or less
(e.g., 400 mm.sup.2 or less, 300 mm.sup.2 or less, 200 mm.sup.2 or
less, 100 mm.sup.2 or less, 50 mm.sup.2 or less, 30 mm.sup.2 or
less, 20 mm.sup.2 or less, 10 mm.sup.2 or less, 5 mm.sup.2 or less,
3 mm.sup.2 or less, 1 mm.sup.2 or less, 0.25 mm.sup.2 or less).
[0113] Returning to FIG. 3, due to the symmetric arrangement of
beams 174 and 176 with respect to prism 122, a total path length of
the radiation in prism 122 is 2 g. In certain embodiments, the
total path length can be 10 mm or less (e.g., 9 mm or less, 8 mm or
less, 7 mm or less, 6 mm or less, 5 mm or less, 4 mm or less, 3 mm
or less, 2 mm or less, 1 mm or less, 0.5 mm or less).
[0114] Prism 122 is positioned within protrusion 166 so that the
exposed surface 122a of prism 122 is substantially integral with an
outer surface of measurement device 100. In other words, prism 122
provides a window in the outer surface of measurement device 100
that permits incident radiation generated within the enclosure to
interact with sample 190. The positioning of prism 122 relative to
enclosure 156 permits contact between prism 122 and sample 190, and
also ensures that the interior of enclosure 156 (e.g., the portion
of enclosure 156 that includes the optical assembly) is not exposed
to or contaminated by sample 190.
[0115] Referring again to FIG. 1, prism 122 is mechanically
isolated from the optical assembly mounted on assembly support 152
within enclosure 156. Support base 204 and mounting plate 202, each
of which contacts prism 122, are also mechanically decoupled from
assembly support 152 and the optical elements mounted thereon. The
mechanical isolation of prism 122 reduces coupling of mechanical
perturbations into the optical assembly. For example, when prism
122 is placed in contact with sample 190, mechanical vibrations can
be induced in prism 122 due to the contact. If transmitted to the
optical assembly, the vibrations could, for example, displace
certain optical elements from alignment. By decoupling prism 122
and the optical assembly mounted on assembly support 152,
disruption of the alignment of the optical components of
measurement device 100 is reduced or eliminated.
[0116] FIG. 5 shows a simplified side cross-sectional view of
measurement device 100. Certain elements of measurement device 100
are not shown in FIG. 5 for clarity. Assembly support 152 is
mounted on support legs 222, which are connected to an inner
surface of hermetic enclosure 224. Hermetic enclosure 224 encloses
the optical assembly mounted on support 152, and includes a window
220 that permits radiation beam 174 to leave hermetic enclosure
224, and permits radiation beam 176 to enter hermetic enclosure
224.
[0117] Hermetic enclosure 224 is hermetically sealed and mounted to
enclosure 156 via posts 226. The remaining interior portion of
enclosure 156, including protrusion 166, includes a liquid-proof
seal but not necessarily a hermetic seal. There are a number of
advantages provided by the interior architecture of measurement
device 100. As discussed above, for example, prism 122 is
mechanically decoupled from the optical assembly mounted to
assembly support 152, which prevents transmission of
large-amplitude mechanical perturbations between prism 122 and
support 152 (and the components thereon).
[0118] In addition, in some embodiments, a coating 154 can be
disposed on one or more inner surfaces of enclosure 156 to further
reduce the amplitude of any mechanical perturbations--in
particular, those that arise from handling measurement device
100--and to reduce or prevent transmission of perturbations to the
elements of the optical assembly. Coating 154 can be formed from
elastic materials such as silicone rubber, for example. In certain
embodiments, a thickness of coating 154 is 0.3 mm or more (e.g.,
0.5 mm or more, 0.7 mm or more, 1.0 mm or more, 1.5 mm or more, 2.0
mm or more, 2.5 mm or more, 3.0 mm or more, 4.0 mm or more).
[0119] During use, the potential exists for the exposed surface
(e.g., surface 122a) of prism 122 to become contaminated with
sample residues in such a way that surface 122a cannot be easily
cleaned. In some cases, prism 122 can also become damaged (e.g.,
scratched) when prism 122 is used to apply pressure to samples.
Contamination or damage to prism 122 may make it necessary to
replace prism 122 by opening enclosure 156. However, by providing a
separate hermetically sealed enclosure 224, exposure of the optical
assembly mounted to assembly support 152 can be avoided, so that
potential environmental contaminants and mechanical disturbances do
not affect the optical components within hermetic enclosure 224.
Following replacement and/or cleaning of prism 122, enclosure 156
can again be sealed with a liquid-proof seal; throughout the repair
process, enclosure 224 remains hermetically sealed.
[0120] Enclosure 156 typically has a handheld form factor, so that
measurement device 100 functions as a handheld infrared
spectrometer, and in particular, as a handheld Fourier transform
infrared spectrometer. FIG. 6 shows a schematic diagram of
enclosure 156 of measurement device 100. In some embodiments,
enclosure 156 can include regions of narrowed width 232 that are
positioned and dimensioned to fit the hand of a system operator, to
facilitate operation of device 100 as a handheld device. In certain
embodiments, enclosure 156 can also include one or more
shock-absorbing external protrusions 230. The shock-absorbing
external protrusions 230 can be formed from an elastic material
such as rubber, for example, and are configured to reduce or
eliminate the transmission of mechanical vibrations to the
components within enclosure 156, and generally to protect the
components of measurement device 100.
[0121] Enclosure 156 can be formed from a variety of different
materials. In some embodiments, enclosure 156 is formed from a
hard, lightweight, durable material such as a hard plastic
material. In certain embodiments, enclosure 156 can be formed from
materials such as aluminum, acrylonitrile butadiene styrene (ABS)
plastic, polycarbonate, and other engineering resin plastics with
relatively high impact resistance. In general, the durable material
that is used to form enclosure 156 and the shock-absorbing external
protrusions 230 together contribute to enclosure 156 being a rugged
enclosure, configured to protect various elements positioned
therein.
[0122] In some embodiments, enclosure 156 can also include a
shoulder strap 231, a portion of which is shown in FIG. 6. In
addition or in the alternative to shoulder straps, enclosure 156
can include a variety of other features such as protruding handles,
recessed handles, clips for attaching enclosure 156 to clothing or
to other supports, and other devices that enhance the portability
of enclosure 156.
[0123] Referring again to FIG. 1, enclosure 156 has a maximum
dimension d. In some embodiments, d is 35 cm or less (e.g., 30 cm
or less, 28 cm or less, 26 cm or less, 24 cm or less, 22 cm or
less, 20 cm or less, 18 cm or less). In certain embodiments, a
volume of enclosure 156 is less than 750 cm.sup.3 (e.g., less than
600 cm.sup.3, less than 500 cm.sup.3, less than 400 cm.sup.3, less
than 350 cm.sup.3, less than 300 cm.sup.3, less than 250 cm.sup.3,
less than 200 cm.sup.3, less than 175 cm.sup.3, less than 150
cm.sup.3). In some embodiments, a total mass of measurement device
100 can be 2 kg or less (e.g., 1.8 kg or less, 1.6 kg or less, 1.4
kg or less, 1.2 kg or less, 1.0 kg or less, 0.8 kg or less, 0.6 kg
or less, 0.4 kg or less).
[0124] In some embodiments, measurement device 100 can also include
a support structure that is configured to connect to enclosure 156
and to support the enclosure during sample measurements. FIG. 7
shows a schematic diagram of a support structure 300 that includes
a base 302 and a mounting member 304. Support structure 300
includes an attachment mechanism 308 positioned on mounting member
304 and configured to connect to enclosure 156. Base 302 includes a
stage 310, and a depressed sample region 312, configured to support
a sample, is positioned in stage 310 in vertical alignment with
protrusion 166. Mounting member 304 permits translation of
enclosure 156 in a direction indicated by arrow 314 (e.g.,
substantially perpendicular to a plane that includes stage 310), so
that prism 122 can be brought into contact with a sample positioned
in sample region 312. In some embodiments, sample region 312 can
include alignment marks 318 that guide a system operator in the
placement of a sample within sample region 312 to ensure good
contact between the sample and an exposed surface of prism 122.
[0125] Typically, support structure 300 is formed of a hard plastic
material, for example, and structure 300 can be formed from the
same material as enclosure 156. In some embodiments, support
structure can be formed from a material other than plastic, such as
aluminum and/or stainless steel.
[0126] In certain embodiments, support structure 300 can be a
portable support structure. For example, as shown in FIG. 7, base
302 and mounting member 304 are joined at hinge 306. When not in
use, support structure can be collapsed by folding mounting member
304 relative to base 302, e.g., by rotating mounting member 304
relative to base 302 in the direction indicated by arrow 316.
[0127] Support structure 300 can be used, for example, for
effectively hands-free operation of measurement device 100. By
connecting enclosure 156 to mounting member 304, both hands of a
system operator are free to handle and position a sample 190, for
example. Measurement and identification of the sample can then be
initiated with a press of a single key on input device 138 by the
system operator.
[0128] As mentioned above, applying pressure to a sample during
analysis can improve a signal-to-noise ratio in measurements of a
reflected radiation beam, and can enable measurement of certain
samples which would otherwise yield inconclusive results in the
absence of direct contact with the prism 122 of the measuring
device 100 and/or the application of compressive force to sample
190. In addition, crushing a sample of a solid material can provide
a substantially homogenous structure (e.g., crushing a sample to
reduce the size of particles of the material being analyzed below a
specific maximum particle size and spreading the particles evenly
across the prism) which can also improve the signal-to-noise ratio
in measurements of a reflected radiation beam.
[0129] In some embodiments, a sample preparation device 502 can be
configured to prepare samples of solid materials for analysis as
well as to support an embodiment of measuring device 100. FIG. 14A
shows the sample preparation device 502 placed on a flat surface
510 (e.g., a tabletop) and receiving and supporting an embodiment
of the measuring device 100. FIGS. 14B and 14C show views of a
portion of the sample preparation device 502 (cross-section) and
the measuring device 100 (side-view) in use together at different
scales. FIG. 15 and FIG. 16 show the sample preparation device 502
and the measuring device 100 separately.
[0130] The sample preparation device 502 includes a protective boot
512 disposed around a housing 514. The housing 514 includes an open
end with a cavity 540 which is sized and configured to receive the
end of measuring device 100 from which an optical interface 122
(e.g., a prism in the illustrated embodiment) extends. The housing
514 defines an aperture 520 extending through the housing 514. The
aperture 520 receives a sample dish 516. In some embodiments, a
seal 554 (e.g., an o-ring) limits the movement of material between
the sample dish 516 and the housing 514. In some cases, a lubricant
(e.g., a silicon-based grease) is applied to the seal 554.
[0131] A sample interface 518 is press-fit within a central
aperture in the sample dish 516. In some embodiments, an adhesive
is used in addition to or as an alternative to the press-fit
attachment of the sample interface 518 within the central aperture
of the sample dish 516. When the measuring device 100 is placed in
the sample preparation device 502, the sample interface 518 of the
sample dish is aligned with the prism 122 of the measuring device
100. The sample preparation device 502 also includes latches 542
configured to engage the measuring device 100 when the measuring
device is inserted into sample preparation device 502 to crush and
analyze a sample 534 of solid material (see FIG. 14B). The rounded
upper corners of the sample interface are thought to be more
resistant to cracking due to high pressures that are present during
use than corners formed at right angles.
[0132] The sample dish 516 has a concave surface 522 extending
laterally outward around the sample interface. The sample interface
518 extends axially upwards from the sample dish 516 When the
sample preparation device is placed on a substantially horizontal
surface for use, the outer edges of concave surface 522 extend
upwards (e.g., farther from the flat surface 510) farther than
sample interface 518. The sample interface 518 can extend axially
between about 0.40 mm and 1.0 mm (e.g., more than about 0.50 mm,
0.60 mm, or 0.75 mm and/or less than about 0.90 mm, 0.75 mm, or
0.60 mm) from the point at which the sample interface 518 contacts
the concave surface 522 of the sample dish 516. In the illustrated
embodiment, the sample interface extends a distance d1 (see FIG.
14B) of approximately 0.55 mm from the point at which the sample
interface 518 contacts the concave surface 522 of the sample dish
516. In use, a small portion of the sample to be analyzed is placed
on the sample interface 518.
[0133] Terms of relative orientation such as "upper", "up",
"lower", and "down" are used for ease of description and refer to
relative position of components when the sample preparation device
is placed on horizontal flat surface as shown in FIGS. 14A and 14B.
These terms do not imply any absolute orientation of the sample
preparation device.
[0134] The sample interface 518 has a hardened surface (e.g., upper
face 524) which is resistant to scratches that might result from
contact with prism 122. In the illustrated embodiment, the sample
interface 518 is formed of sapphire. In some embodiments, the
sample interface 518 comprises (e.g., is formed of or has a surface
layer of) other materials such as, for example, diamond, ruby, or
materials with a hardness of at least 8 on the Mohs scale. The
upper face 524 has an area of between about 5.0 and about 7.0
square millimeters (e.g., more than about 5.25, 5.5, or 5.75 square
millimeters and/or less than about 6.75, 6.5, or 6.25 square
millimeters). In the illustrated embodiment, the upper face has an
area of approximately 6.1 square millimeters.
[0135] Use of a projection with a small contact area allows a
relatively small force to provide a relatively high pressure on the
sample being analyzed. This can enable a user to relatively easily
insert the measuring device 100 into place in the sample
preparation device 502.
[0136] In some embodiments, a protective liner (not shown) is
placed between the sample dish 516/sample interface 518 and the
measuring device 100. The protective liner can be a thin disk
(e.g., a plastic/Teflon.RTM./Mylar.RTM. disk) whose shape generally
conforms with the upper surface 522 of the sample dish 516 and the
sample interface 518. The protective liner can be disposable (e.g.,
replaceable after use with a certain number of samples).
[0137] The sample dish 516 has a first section 526, adjacent the
upper surface 522, and a second section 528, spaced apart from the
upper surface 522, with different outer dimensions. The first
section 526 has a characteristic outer dimension which is smaller
than the characteristic outer dimension of the second section 528.
In the illustrated example, the sample dish is substantially
cylindrical in form and the first section 526 is a cylinder whose
circumference is less than the circumference of the second section
528. There is a sharp transition or step between the first section
526 and the second section 528 of the sample dish.
[0138] The aperture 520 has a first section 530 and a second
section 532 which are, respectively, sized to slidably receive the
first and second sections 526, 528 of the sample dish 516. The
first section 530 of the aperture 520 is smaller than the second
section 532 of the aperture 520 with a sharp transition or step
between the first section 530 and the second section 532 of the
aperture 520. A resilient member 536 biases the sample dish 516
towards the first section 530 of the aperture 520 such that the
step between sections 526, 528 of the sample dish 516 engages the
step between sections 530, 532 of the aperture 520 in the absence
of outside forces (e.g., in the absence of the measuring device
100). The resilient member 536 can be, for example, a coil spring,
a leaf spring, or a hydraulic cylinder. In the illustrated
embodiment, the resilient member 536 is a coil spring which is
located in the aperture 520 between the sample dish 516 and a
retainer 538 (e.g., a cylindrical retainer with spiral threads on
its outer surface). The resilient member 536 is selected to provide
a force on the sample dish and/or a specific pressure between the
sample interface 518 and the prism 122 on the measuring device 100
when the measuring device 100 is pressed into the cavity 540. In
some embodiments, the sample unit is fixed in place in the housing
and a resilient member biases the measuring device towards the
sample unit.
[0139] In the illustrated embodiment, the housing 514 is inverted
(e.g., placed with the cavity 540 downward) for installation of the
sample dish 516, the resilient member 536, and the retainer 538.
The sample dish 516 is then placed in the aperture 520 with the
first section 526 of the sample dish 516 oriented towards the first
section 530 of the aperture 520 such that such that the step
between sections 526, 528 of the sample dish 516 rests on the step
between sections 530, 532 of the aperture 520. The coil spring 536
is then placed in the aperture 520 with one end of the coil spring
536 resting on the sample dish 516. The retainer 538 is pressed
against the other end of the coil spring 536 to compress the coil
spring 536 until the threads on the outer surface of the retainer
538 engage corresponding threads on the inner wall of the aperture
520. The retainer 538 is then screwed into place.
[0140] After the sample dish 516, the resilient member 536, and the
retainer 538 are installed in the housing 514, the housing 514 is
placed into protective boot 512. The housing 514 can be held in
place in the protective boot 512 by press-fit engagement between
the housing 514 and the protective boot 512. The protective boot
512 can provide a high-friction, slip resistant surface on the base
of the sample preparation device 502 to help hold the sample
preparation device 502 in place (e.g., when placed on a somewhat
inclined surface). The presence of the protective boot 512 can
prevent the retainer 538 from unscrewing from the housing 514. The
protective boot 512 can be removed from the housing 514 while the
sample preparation device is being cleaned or when it is necessary
to replace internal parts (e.g., the resilient member 536) of the
sample preparation device 502. The protective boot 512 can be made
of a durable, easy to clean material such as rubber.
[0141] The latches 542 of the sample preparation device 502 are
mounted on housing 514 to pivot around a pin 544. Resilient members
546 (e.g., coil springs) bias an upper end 548 of each latch 542
towards the cavity 540 defined by the housing 514. When a user
presses the measuring device 100 into the cavity 540, contact with
the measuring device 100 forces the upper ends 548 of latches 542
outward until the measuring device 100 is positioned to analyze a
sample of solid material in the sample dish 516. In this position,
the upper ends 548 of the latches 542 engage latch hooks 550 on
opposite sides of the measuring device 100 to latch the measuring
device 100 into place. The user can release the measuring device
100 from the sample preparation device by pressing inward on the
lower ends 552 of the latches 542 to rotate the upper ends 548 of
the latches 542 out of engagement with the latch hooks 550 on the
measuring device 550.
[0142] The sample preparation device 502 is sized and configured to
stably support the measuring device 100 when the measuring device
100 is snapped into place in the sample preparation device 502. In
the illustrated embodiment, the sample preparation device has a
height h1 of approximately 2.7 inches, a width w1 of approximately
2.8 inches, and depth d2 of approximately 2.3 inches and weighs
approximately 1.4 pounds.
[0143] The embodiment of the measuring device 100 illustrated in
FIG. 16 has inner components substantially similar to the inner
components of the measuring device 100 described with reference to
FIGS. 1-5. The enclosure or housing 156 supports the electronic
display 136 and the input device 138 which includes multiple keys
for controlling operation of the measuring device 100 (e.g., menu
driven operation using menus displayed on electronic display 136).
The presentation of graphical content (e.g., text and/or icons) on
display 136 is controllable with at least a first mode in which
text and/or icons being displayed are oriented with the relative
top of the display 136 being the side of the display 136 towards
the input device 138 and a second mode in which text and/or icons
being displayed are oriented with the relative top of the display
136 being the side of the display 136 towards the prism 122. During
hand-held use (e.g., separate from sample preparation device 502),
it is typically easier for the user to read information displayed
in the second mode. When the measuring device 100 is used with
sample preparation device 502, it is typically easier for the user
to read information displayed in the first mode.
[0144] The measuring device 100 includes latch hooks 550 which are
configured to engage the latches 542 when the measuring device 100
is inserted into the sample preparation device 502. The measuring
device 100 also includes features 558 extending laterally outward
on each side of the prism 122. The protruding features 558 on the
measuring device 100 are configured to engage recesses 556 in the
housing 514 of the sample preparation device 502 to align and guide
the measuring device 100 into place when the measuring device 100
is inserted into the sample preparation device 502.
[0145] The prism 122 has a contact face 560 with an area of between
about 2.0 and about 4.0 square millimeters (e.g., more than about
2.25, 2.50, or 2.75 square millimeters and/or less than about 3.75,
3.50, or 3.25 square millimeters). The prism 122 and an associated
prism housing 561 extend outward from adjacent parts of the
measuring device 100. In the illustrated embodiment, the prism 122
is flush mounted within the prism housing 561 (i.e., the outer
surfaces of the prism 122 and the prism housing are substantially
co-planar). In the illustrated embodiment, the contact face 560 of
the prism has an area of approximately 3.2 square millimeters. The
prism 122 can be formed from a relatively hard material such as
diamond to limit the possibility that contact with samples and/or
other objects will mar the contact face 560 of the prism 122.
[0146] The measuring device 100 is configured for handheld use. In
the illustrated embodiment, the measuring device 100 has a height
h2 of approximately 8 inches, a width w2 of approximately 4.5
inches, and depth d3 of approximately 2 inches and weighs
approximately 3 pounds. When the measuring device 100 is snapped
into place in the sample preparation device 502, the center of
gravity of the combined unit remains above the bottom side 562 of
the housing 514 until the combined unit is tilted more than about
15 degrees
[0147] In operation, a user sets the sample preparation device 502
on a substantially flat surface and places a small sample 534 of a
solid material to be analyzed. The user then inserts the measuring
device 100 into the sample preparation device 502. Contact between
protruding features 558 on the measuring device 100 and recesses
556 in the housing 514 of the sample preparation device 502 align
and guide the measuring device 100 into place as the measuring
device 100 is pressed downward. Contact with the measuring device
100 forces the upper ends 548 of latches 542 outward until the
measuring device 100 is in position at which point the latches 542
engage the latch hooks 550 on the measuring device 100.
[0148] As shown on FIG. 14C, during insertion, the sample 534 is
compressed between the measuring device 100 and the sample
preparation device 502. In particular, the portion of the sample
534 located above the sample interface 518 is compressed between
the prism 122/prism housing 561 of the measuring device 100 and the
sample interface 518 of the sample preparation device 502. Excess
portions of sample 534 squeezed out from between the prism
122/prism housing 561 of the measuring device 100 and the sample
interface 518 can fall into the sample dish 516. The size of the
sample 534 should be limited to reduce the likelihood that enough
sample builds up in the sample dish 516 to bridge between the
sample dish 516 and the measuring device as this could reduce the
pressure between the prism 122 and the sample interface 518.
[0149] The sample dish 516 and sample interface 518 can move
axially downward as the measuring device 100 is inserted into the
sample preparation device 502. After the user releases the
measuring device 100 and the measuring device 100 is being held in
place by the latches 542, the sample dish 516 and sample interface
518 have been displaced downward. Because of this displacement, the
resilient member 536 exerts a force pressing the sample dish 516
and the sample interface 518 towards the prism. The amount of
pressure applied to the sample between the sample interface 518 and
the prism 122 is a function of the smaller of the area of the prism
contact face/prism housing and the area of the upper face 524 of
the sample interface 518, the distance that the sample dish is
displaced, and the characteristics of the resilient member 536. For
example, in the illustrated embodiment, the pressure applied to the
portion of the sample between the can be estimated as
P=kd/a
[0150] where P is pressure; [0151] d3 is the distance that the
sample dish 516 is displaced; [0152] k is the spring rate of the
coil spring 536; and [0153] a is the area of the upper face 524 of
the sample interface 518. The resilient member 536 is selected to
provide a specific pressure between the sample interface 518 and
the prism 122 on the measuring device 100 when the measuring device
100 is pressed into the cavity 540. For example, the resilient
member 536 can be configured to apply between about 10 and 30
pounds of force when the measuring device 100 is inserted in the
sample preparation device 502. A pressure on a sample adjacent the
prism 122 of between about 1,000 and 3,000 pounds per square inch
(e.g., less than 2,500, 2,000, and 1,500 pounds per square inch
and/or more than 1,500, 2,000, and 2,500 pounds per square inch)
has been found to improve a signal-to-noise ratio in measurements
of a reflected radiation beam for samples including, for example,
fine to granular powders, flat sheets of plastic, flakes, beads,
crystals, and rocks. Pressures below 1,000 pounds per square inch
may improve a signal-to-noise ratio in measurements of a reflected
radiation beam for some samples (e.g., samples with a smaller
initial particle size and/or less rigid initial structure and
distribution). For some types of samples, it may be desirable to
configure the sample preparation device 502 to provide higher
pressures. However, increasing the pressures adjacent the prism 122
by increasing the spring force may make it difficult to insert the
measuring device 100 into the sample preparation device. Increasing
the pressures adjacent the prism 122 by decreasing the contact area
(e.g., decreasing the size of the contact face 560 of the prism 122
and/or the upper face 524 of the sample interface 518) may make it
more likely that contact between the prism 122 and the sample
interface 518 will damage one or both of these components.
[0154] After use, the sample preparation device 502 can be cleaned
using alcohol wipes. After use with substances which are
potentially hazardous at low level, the sample preparation device
can be immersed bleach solution.
[0155] The sample preparation device 502 can also be used to store
the measuring device 100 when the measuring device 100 is not being
used.
[0156] In the illustrated embodiment, the area a of the upper face
524 of the sample interface 518, is approximately 6.1 square
millimeters. Because the area a is smaller than the combined area
of the prism/prism housing contact face, the area a of the upper
face 524 of the sample interface 518 controls how much pressure
develops between the sample interface 518 and the prism 122. In the
illustrated embodiment, the resilient member 536 is a stainless
steel coil spring commercially available from Associated Spring
Raymond (www.asraymond.com) catalog number C0975-074-1000-S with a
spring rate of about 23.41 pounds per inch. The spring 536 is
assembled preloaded to deflect 0.33 inches. When inserted into the
sample preparation device 502, the measuring device 100 displaces
the sample dish and additionally deflects the spring 536 a distance
d3 of approximately 0.09 inches. Other springs with lower or higher
spring rates can be used.
[0157] When the measuring device 100 is inserted into the sample
preparation device 502, the pressure, P, on the sample adjacent the
contact face 560 of the prism was calculated to be approximately
1,000 pounds per square inch. The illustrated embodiments of the
measuring device 100 and the sample preparation device 502 have
been used in combination to successfully analyze solid samples
including fine to granular powders, flat sheets of plastic, flakes,
beads, crystals, and rocks.
[0158] Although described for use with solid samples, the
illustrated measuring device 100 and sample preparation device 502
could be used for analysis of liquid samples. However, in the
absence of the particle size and distribution issues associated
with solid samples, the measuring device 100 can be used to analyze
liquid samples without the sample preparation device 502 by placing
the prism 122 in the material to be analyzed if the material is
present in a large volume (e.g., in a puddle). The measuring device
100 can also be used to analyze liquid samples by placing the
measuring unit with the prism upwards and placing a droplet of the
sample to be analyzed on the contact face 560 of the prism 122.
[0159] The preceding discussion has focused on the use of infrared
absorption information to identify a sample. In some embodiments,
sample information in addition to infrared absorption information
can be used to identify the sample. For example, measurement device
100 can be configured to cooperate with other scanning systems to
identify samples of interest. Suitable other scanning systems can
include, for example, handheld and non-handheld Raman scanning
systems. To identify a sample, the sample can first be scanned with
a Raman scanning system that is configured to determine an identity
of the sample based on Raman scattering information about the
sample. The identity determined by the Raman scanning system is
then transmitted to measurement device 100 and received via
communication interface 142.
[0160] Measurement device 100 is also configured to separately
determine an identity of the sample based on infrared absorption
information. If the identities determined via infrared absorption
information and Raman scattering information agree, measurement
device 100 reports a successful identification to a system
operator. If the identities do not agree, measurement device 100
reports a failed identification. More generally, both the Raman
scanning system and measurement device 100 can be configured to
determine an identity of the sample, and a numerical score or
metric that is related to an extent of correspondence between the
measured sample information and reference information for the
sample. Measurement device 100 can then determine, based on the
identities reported and the values of the metrics, whether the
identification process was successful or not, and to what extent
the reported identity of the sample is trustworthy.
[0161] In certain embodiments, an infrared absorption spectrometer
and a Raman spectrometer can be combined in a single handheld
instrument. FIG. 8 shows a schematic diagram of a measurement
device 400 that includes an infrared scanning subsystem and a Raman
scanning subsystem. The components of the infrared scanning
subsystem have been discussed previously, and function in similar
fashion in the embodiment shown in FIG. 1. In addition to these
components, measurement device 400 also includes a radiation source
402, a beamsplitter 404, a coupling window 408, and a radiation
analyzer 406. Radiation source 402 and radiation analyzer 406 are
in electrical communication with processor 134 via communication
lines 162j and 162k.
[0162] As shown in FIG. 8, protrusion 166--which includes prism
122--forms a first aperture, and the infrared scanning subsystem is
configured to direct incident radiation to a sample when the sample
is in contact with prism 122 to determine infrared absorption
information about the sample.
[0163] Coupling window 408 forms a second aperture. The Raman
scanning subsystem is configured to direct incident radiation to
the sample when the sample is positioned in proximity to coupling
window 408 to determine Raman scattering information about the
sample. Radiation source 402, after receiving a suitable control
signal from processor 134, generates incident radiation 410. A
portion of incident radiation 410 reflects from dichroic
beamsplitter 404 and leaves enclosure 156 through coupling window
408. Radiation 410 is incident on the sample, and a portion of the
radiation is scattered by the sample as scattered radiation 412.
The scattered radiation (or a portion thereof) passes through
dichroic beamsplitter 404 and enters radiation analyzer 406. Once
inside radiation analyzer 406, reflected radiation 412 is
manipulated (e.g., by dispersing scattered radiation 412 into a
plurality of wavelength components) and measured (e.g., using one
or more photoelectric or CCD detectors) to derive Raman scattering
information about the sample. Radiation analyzer 406 can include
one or more dispersive elements such as gratings and/or prisms,
various lenses and/or mirrors for collimating, focusing, and
re-directing radiation, or more filter elements for reducing
radiation intensity, and one or more beamsplitting elements for
dividing radiation beams into multiple beams. Radiation analyzer
406 can also include various types of radiation detectors, and a
processor.
[0164] The measured Raman scattering information is then
transmitted to processor 134. Suitable methods for measuring Raman
scattering information, and suitable systems and components
thereof, are described, for example, in U.S. patent application
Ser. No. 11/837,284 entitled "OBJECT SCANNING AND AUTHENTICATION"
by Kevin J. Knopp et al., filed on Aug. 10, 2007, the entire
contents of which are incorporated by reference herein.
[0165] Typically, to perform a measurement on a sample, the sample
is first positioned in proximity to coupling window 408 and Raman
scattering information about the sample is measured. Then,
measurement device 400 is re-oriented (or the sample is moved) so
that the sample contacts the exposed surface of prism 122, and
infrared absorption information about the sample is measured. The
Raman scattering and infrared absorption information is transmitted
to processor 134, and the processor identifies the sample based on
the two types of information.
[0166] Processor 134 can determine an identity of the sample using
a variety of different algorithms that process the Raman scattering
information and infrared absorption information about the sample.
In some embodiments, for example, processor 134 can be configured
to compare the Raman scattering information about the sample to a
database of reference Raman scattering information stored in
storage unit 140 for a variety of samples, to determine whether the
sample Raman scattering information matches reference Raman
scattering information for a particular substance. If a match is
found, a numerical score or metric can be calculated which reflects
an extent of correspondence between the sample and reference Raman
scattering information. As discussed previously, the stored
reference Raman scattering information can be updated periodically
via communication interface 142.
[0167] Similarly, processor 134 can compare the sample infrared
absorption information to reference infrared absorption information
stored in storage unit 140 to determine whether the sample infrared
absorption information matches reference information for a
particular substance. If a match is found, a numerical score or
metric can be calculated which reflects an extent of correspondence
between the sample and reference infrared absorption
information.
[0168] Processor 134 then compares the substances matched by the
sample Raman scattering information and infrared absorption
information. If the matched substances are the same for each,
processor 134 outputs a signal to display 136 that indicates to a
system operator a successful identification of the sample. The
signal can include the identity of the sample, and one or more
metrics that are calculated from the comparisons of the sample and
reference Raman scattering information and/or infrared absorption
information. The one or more metrics can provide an indication of
the extent of correspondence between sample and reference Raman
scattering information and/or sample and reference infrared
absorption information, for example. Algorithms and suitable
metrics for comparing sample and reference Raman scattering
information and/or sample and reference infrared absorption
information are generally disclosed, for example, in U.S. Pat. No.
7,254,501 entitled "SPECTRUM SEARCHING METHOD THAT USES
NON-CHEMICAL QUALITIES OF THE MEASUREMENT", issued on Aug. 7, 2007,
the entire contents of which are incorporated by reference
herein.
[0169] Returning to FIG. 1, in some embodiments, measurement device
100 can include only an infrared scanning subsystem (e.g., no Raman
scanning system), and processor 134 can be configured to receive
sample Raman scattering information measured by another device. For
example, a Raman scanning device can be configured to scan samples
and transmit Raman scattering information obtained from the samples
over a wired or wireless network to measurement device 100.
Measurement device 100 can be configured to receive the sample
Raman scattering information via communication interface 142, and
to compare the sample Raman scattering information to reference
Raman scattering information stored in storage unit 140 to
determine an identity of the sample. Measurement device 100 can
also be configured to measure sample infrared absorption
information as discussed above, and to compare the infrared
absorption information about the sample to reference infrared
absorption information to determine an identity of the sample.
Results from the comparisons of the sample and reference Raman
scattering information and infrared absorption information can then
be combined in the manner disclosed above.
[0170] In certain embodiments, processor 134 can be configured to
automatically determine (or accept similar directions from a system
operator) whether to use only Raman scattering information about
the sample to determine the sample's identity, whether to use only
infrared absorption information about the sample to determine the
sample's identity, or whether to use a combination of both Raman
scattering information and infrared absorption information.
Typically, for example, processor 134 can be configured to assign
relative weights ranging from 0 to 1 to the sample Raman scattering
information and infrared absorption information. The assignment of
a weight of 0 corresponds to non-use of the information.
[0171] Certain types of samples, for example, are aqueous-based, or
include large numbers of alcohols and/or hydroxyl (-OH) groups. In
infrared absorption spectra, --OH groups typically exhibit a
strong, broad, featureless stretching band at about 3300 cm.sup.-1.
This broad band can obscure other spectral features which could
otherwise be used to identify the sample. Therefore, in some
embodiments, processor 134 can be configured to reduce reliance on
infrared absorption information when identifying the sample, and to
use primarily Raman scattering information to identify the sample,
since Raman scattering spectra typically do not include such broad
--OH bands (and are not sensitive to water). FIGS. 9A and 9B show
examples of infrared absorption and Raman scattering information,
respectively, measured for a sample that includes a 3% hydrogen
peroxide solution in water. The infrared absorption spectrum
includes a broad, featureless --OH band that corresponds to both
water and hydrogen peroxide. The Raman scattering spectrum includes
a narrow band that corresponds approximately only to hydrogen
peroxide. In general, the use of infrared absorption information
can be reduced relative to Raman scattering information by
processor 134 to circumvent a number of troublesome infrared
spectral features, including --OH stretching bands as disclosed
above.
[0172] Certain types of samples exhibit large background
fluorescence, which reduces the accuracy of measured Raman
scattering information. Typically, for example, the large
background fluorescence appears in Raman spectra as a broad,
featureless band that can obscure underlying peaks, making
identification of the sample on the basis of the Raman scattering
information difficult. Processor 134 can be configured to reduce
reliance on Raman scattering information when identifying the
sample, and to use primarily infrared absorption information to
identify the sample, since infrared absorption spectra are not
typically perturbed by background fluorescence. FIGS. 10A and 10B
show examples of infrared absorption and Raman scattering
information, respectively, measured for a sample of isopropanol.
The Raman spectrum of isopropanol includes a featureless, broad
fluorescence band that nearly obscures the underlying bands. The
infrared absorption spectrum includes a relatively small --OH
stretching band that does not overwhelm the spectrum, and several
well-resolved bands at energies lower than 3000 cm.sup.-1 that can
be used to identify the sample. In general, the use of Raman
scattering information can be reduced relative to infrared
absorption information by processor 134 to circumvent a number of
troublesome Raman spectral features, including fluorescence bands
as disclosed above.
[0173] In some embodiments, both Raman scattering information and
infrared absorption information can be used to identify a sample in
complementary fashion. FIGS. 11A and 11B show examples of infrared
absorption and Raman scattering information, respectively, measured
for a sample of DEET pesticide. Each of the Raman scattering and
infrared absorption spectra includes multiple well-resolved bands,
so that both the Raman scattering and infrared absorption
information can be used by processor 134 to determine an identity
of the sample.
[0174] Referring again to FIG. 8, radiation source 402 can include
one or more of a variety of sources including, for example, laser
diode sources, light-emitting diode sources, and laser sources.
Incident radiation 410 provided by source 402 generally includes a
distribution of radiation wavelengths. In some embodiments, a
center wavelength of the distribution is 800 nm or less (e.g., 700
nm or less, 600 nm or less, 500 nm or less, 450 nm or less, 400 nm
or less, 350 nm or less, 300 nm or less, 250 nm or less). In
particular, because Raman scattering cross-sections for various
samples generally increase with decreasing wavelength, greater
Raman scattering signal strength can be obtained by generating
incident radiation 410 with a center wavelength less than 450
nm.
[0175] The intensity of incident radiation 410 can generally be
selected as desired to generate a Raman scattering signal from the
sample. Typically, the intensity of incident radiation 410 can be
tens or hundreds of milliwatts, for example. However, in certain
embodiments (such as, for example, embodiments where a center
wavelength of incident radiation 410 is less than 450 nm), an
intensity of incident radiation 410 can be 20 mW or less (e.g., 10
mW or less, 5 mW or less, 4 mW or less, 3 mW or less, 2 mW or less,
1 mW or less, 0.5 mW or less). In some embodiments, relatively low
intensities can be used to prevent possible detonation of unknown
substances due to heating of the substances by radiation 410.
[0176] In some embodiments, measurement devices can include both
infrared and Raman scanning subsystems, and both the infrared and
Raman subsystems can be configured to direct incident light to a
sample via prism 122. The subsystems can be configured so that the
incident light from each subsystem interrogates a common region of
the sample, which reduces measured signal noise due to spatial
inhomogeneity of the sample. FIG. 12 shows a measurement device 500
where incident radiation from each of the infrared and Raman
scanning subsystems passes into prism 122 and is incident on sample
190. Many of the components in FIG. 12 have been previously
discussed. Source 402 generates incident radiation beam 410 that is
directed by mirror 420 to enter prism 122 and interact with the
sample via surface 122a. Scattered radiation beam 412 is directed
by mirror 422 to enter radiation analyzer 406. Radiation analyzer
406 disperses wavelength components of scattered radiation beam 412
and measures the dispersed components to determine Raman scattering
information about the sample.
[0177] In the embodiment shown in FIG. 12, both the infrared
scanning subsystem and the Raman scanning subsystem direct incident
light to a common location on sample 190. In addition to reducing
noise due to spatial inhomogeneity in the measured sample
information, the configuration of measurement device 500 shown in
FIG. 12 is simpler than the configuration of measurement device 400
in FIG. 8, requiring fewer apertures. Further, measurements of both
Raman scattering information and infrared absorption from the
sample can be made without re-positioning measurement device 500
relative to sample 190.
[0178] Although the embodiment shown in FIG. 12 is primarily
configured to analyze samples 190 in contact with prism 122, Raman
scanning subsystems can be used to analyze samples that are spaced
apart from the prism 122. For example, it is sometimes useful to be
able to analyze the contents of a bottle (e.g., at an airport
checkpoint). FIGS. 13A and 13B show portions of an optical analysis
device 600 that is generally similar to the optical analysis device
500 shown in FIG. 12 except for the configuration of the Raman
analysis subsystem.
[0179] In optical analysis device 600, source 402 generates
incident radiation beam 410 that is directed by a Raman optical
assembly. With this construction, the output of excitation light
source 402 is collimated through lens 615. A bandpass filter 620
(or combination of multiple bandpass filters 620A, 620B) is used to
pass the laser excitation light and to block spurious signals
associated with the laser and/or other optical components. The
laser excitation light is then reflected by a filter 625, which in
this configuration may be a laser line reflector (at a 40 degree
Angle of Optical Incidence, AOI) and a filter 630 (at a 5 degree
AOI), and then it is focused through lens 635 to excite specimen
190. Although specific AOI values are described for this
illustrative example, the AOI values may vary from one embodiment
to another. In one embodiment, filter 630 can be a long-pass
filter. In this embodiment, laser line reflector 625 can be a
simple reflector to reflect the laser light. After the laser
excitation light has been projected on the specimen, the Raman
signal is re-collimated through lens 635 and passed through filter
630. Alternatively, the Raman signal may pass through multiple
filters (e.g., in addition to passing through filter 630, the Raman
signal may pass through additional filter 645, at a 5 degree AOI).
In one embodiment, additional filter 645 is also a long-pass
filter. When the Raman signal from the specimen is passed though
filter 630, filter 630 can also serve to block the laser line.
Filters 630 and 645 can provide up to >OD10 filtration of the
laser line before the light is redirected through broadband
reflector 650 (at a 45 degree AOI) and focus lens 655 into
radiation analyzer 406. This and other embodiments of the optical
assembly are described in more detail in U.S. Pat. Pub. No.
2005/0248759 which is incorporated herein by reference in its
entirety. In this embodiment, the prism 122 is truncated such that
incident radiation beam 410 passes through a flat face 122d which
is substantially parallel to the exterior surface 122a of the
prism.
[0180] The lens 635 has a focal length 1. A translation mechanism
(not shown) can be operated to move the lens 635 parallel to the
optical axis of the lens 635. In a first position (see FIG. 13A),
the lens 635 focuses incident radiation beam 410 at point
co-located with the exterior surface 122a of the prism 122. A
portion of the radiation is scattered by the sample and the
scattered radiation (or a portion thereof) passes through the
optical assembly and is redirected by the Raman optical assembly to
enter radiation analyzer 406. In a second position (see FIG. 13B),
the lens 635 is moved towards the prism such that the lens 635
focuses incident radiation beam 410 at point past the exterior
surface 122a of the prism 122. In this position, the Raman
subsystem can be used to analyze samples 190 that are spaced apart
from optical analysis device 600.
[0181] The measurement devices disclosed herein can be used for a
variety of sample identification applications. For example, the
measurement devices disclosed herein can be used in airports and
other transportation hubs, in government buildings, and in other
public places to identify unknown (and possibly suspicious)
substances, and to detect hazardous and/or prohibited substances.
Airports, in particular, restrict a variety of substances from
being carried aboard airplanes. The measurement devices disclosed
herein can be used to identify substances that are discovered
through routine screening of luggage, for example. Identified
substances can be compared against a list of prohibited substances
(e.g., a list maintained by a security authority such as the
Transportation Safety Administration) to determine whether
confiscation and/or further scrutiny by security officers is
warranted.
[0182] Law enforcement officers can also use the portable
measurement devices disclosed herein to identify unknown
substances, including illegal substances such as narcotics.
Accurate identifications can be performed in the field by on-duty
officers.
[0183] The measurement systems disclosed herein can also be used to
identify a variety of industrial and pharmaceutical substances.
Shipments of chemicals and other industrial materials can be
quickly identified and/or confirmed on piers and loading docks,
prior to further transport and/or use of the materials. Further,
unknown materials can be identified to determine whether special
handling precautions are necessary (for example, if the materials
are identified as being hazardous). Pharmaceutical compounds and
their precursors can be identified and/or confirmed prior to
production use and/or sale on the market.
[0184] Generally, a wide variety of different samples can be
identified using the measurement devices disclosed herein,
including pharmaceutical compounds (and precursors thereof),
narcotics, industrial compounds, explosives, energetic materials
(e.g., TNT, RDX, HDX, and derivatives of these compounds), chemical
weapons (and portions thereof), household products, plastics,
powders, solvents (e.g., alcohols, acetone), nerve agents (e.g.,
soman), oils, fuels, pesticides, peroxides, beverages, toiletry
items, other substances (e.g., flammables) that may pose a safety
threat in public and/or secure locations, and other prohibited
and/or controlled substances.
[0185] Other embodiments are in the claims.
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