Preparing samples for optical measurement

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.

TECHNICAL FIELD

This disclosure relates to optical measurement and identification of samples.

BACKGROUND

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

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.

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.

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.

Embodiments of the apparatus can include one or more of the following features.

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.

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.

In some embodiments, the projection of the sample unit comprises a material with a hardness of at least 8 on the Mohs scale.

In some embodiments, the projection of the sample unit comprises sapphire, diamond, or ruby.

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.

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.

In some embodiments, wherein the optical interface is a prism.

In some embodiments, the sample receptacle is open to the atmosphere.

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.

In some embodiments, the housing comprises a substantially flat surface opposite the sample unit.

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.

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.

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.

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.

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.

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.

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).

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.

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.

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.

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).

The second radiation source can include a laser diode.

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.

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.

Embodiments of the apparatus can also include any of the other features disclosed herein.

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.

Embodiments of the method can include one or more of the following features.

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.

In some embodiments, compressing the sample comprises automatically controlling force applied to the sample by the device and the optical analysis unit.

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.

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.

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.

Embodiments of the method can also include any of the other method steps disclosed herein, as appropriate.

Embodiments can include one or more of the following advantages.

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.

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.

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).

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.

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.

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.

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.

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.

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.

DETAILED DESCRIPTION

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.

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.

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.

FIG. 1shows a schematic diagram of a measurement device100. Device100includes an optical assembly mounted on an assembly support152that is fixed within an enclosure156. The optical assembly includes: radiation sources102and144; mirrors104,108,110,148,118,120,126,128, and130; beamsplitters106and146; detectors132and150; and prism122. Device100also includes a shaft112, a bushing114, and an actuator116coupled to mirror110, and an electronic processor134, an electronic display136(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 device138, a storage unit140, and a communication interface142. Electronic processor134is in electrical communication with detector132, storage unit140, communication interface142, display136, input device138, radiation sources102and144, detector150, and actuator116, respectively, via communication lines162a-i.

Measurement device100is configured for use as a Fourier transform infrared (FTIR) spectrometer. During operation, radiation168is generated by radiation source102under the control of processor134. Radiation168is directed by mirror104to be incident on beamsplitter106, which is formed from a beamsplitting optical element106aand a phase compensating plate106b, and which divides radiation168into two beams. A first beam170reflects from a surface of beamsplitter106, propagates along a beam path which is parallel to arrow171, and is incident on fixed mirror108. Fixed mirror108reflects first beam170so that first beam170propagates along the same beam path, but in an opposite direction (e.g., towards beamsplitter106).

A second beam172is transmitted through beamsplitter106and propagates along a beam path which is parallel to arrow173. Second beam172is incident on a first surface110aof movable mirror110. Movable mirror110reflects second beam172so that beam172propagates along the same beam path, but in an opposite direction (e.g., towards beamsplitter106).

First and second beams170and172are combined by beamsplitter106, which spatially overlaps the beams to form incident radiation beam174. Mirrors118and120direct incident radiation beam174to enter prism122through prism surface122b. Once inside prism122, radiation beam174is incident on surface122aof the prism122. Surface122aof prism122is positioned such that it contacts a sample of interest190. When radiation beam174is incident on surface122a, a portion of the radiation is coupled into sample190through surface122a. Typically, for example, sample190absorbs a portion of the radiation in radiation beam174.

Radiation beam174undergoes total internal reflection from surface122aof prism122as reflected beam176. Reflected beam176includes, for example, the portion of incident radiation beam174that is not absorbed by sample190. Reflected beam176leaves prism122through surface122c, and is directed by mirrors126,128, and130to be incident on detector132. Under the control of processor134, detector132measures one or more properties of the reflected radiation in reflected beam176. For example, detector132can determine absorption information about sample190based on measurements of reflected beam176.

Typically, the radiation in reflected beam176is measured at a plurality of positions of movable mirror110. Mirrors108and110, together with beamsplitter106, are arranged to form a Michelson interferometer, and by translating mirror110in a direction parallel to arrow164prior each measurement of reflected radiation176, the plurality of measurements of the radiation in reflected beam176form an interferogram. The interferogram includes information such as sample absorption information. Processor134can be configured to apply one or more mathematical transformations to the interferogram to obtain the sample absorption information. For example, processor134can 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.

Movable mirror110is coupled to shaft112, bushing114, and actuator116. Shaft112moves freely within bushing114, and a viscous fluid is disposed between shaft112and bushing114to permit relative motion between the two. Mirror110moves when actuator116receives control signals from processor134via communication line162i. Actuator116initiates movement of shaft112in a direction parallel to arrow164, and mirror110moves in concert with shaft112. Bushing114provides support for shaft112, preventing wobble of shaft112during translation. However, bushing114and shaft112are effectively mechanically decoupled from one another by the fluid disposed between them; mechanical disturbances such as vibrations are coupled poorly between shaft112and bushing114. 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 device100.

To measure the position of mirror110, device100includes a second interferometer assembly that includes radiation source144, beamsplitter146, mirror148, and detector150. These components are arranged to form a Michelson interferometer. During a mirror position measurement operation, radiation source144receives a control signal from processor134via communication line162g, and generates a radiation beam178. Beam178is incident on beamsplitter146, which separates radiation beam178into a first beam180and a second beam182. First beam180reflects from the surface of beamsplitter146and is incident on a second surface110bof mirror110. Second surface110bis positioned opposite first surface110aof mirror110. First beam180reflects from surface110band returns to beamsplitter146.

Second beam182is transmitted through beamsplitter146, reflected by mirror148, and returned to beamsplitter146. Beamsplitter146combines (e.g., spatially overlaps) reflected beams180and182, and the combined beam184is directed to detector150. Detector150receives control signals from processor134via communication line162h, and is configured to measure an intensity of combined beam184. As the position of mirror110changes (e.g., due to translation of mirror110along a direction parallel to arrow164), the intensity of the radiation measured by detector150changes due to interference between first beam180and second beam182in combined beam184. By analyzing the changes in measured radiation intensity from detector150, processor134can determine with high accuracy the position of mirror110.

Position information for mirror110is combined by processor134with measurements of the radiation in reflected beam176to construct an interferogram for sample190. As discussed above, processor134can be configured to apply a Fourier transform to the interferogram to obtain absorption information about sample190from the interferogram. The absorption information can be compared by processor134to reference information (e.g., reference absorption information) stored in storage unit140to determine an identity of sample190. For example, processor134can 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 unit140. If a match is found (e.g., the sample absorption information and the reference information for a particular substance agree sufficiently), then sample190is considered to be identified by processor134. Processor134can send an electronic signal to display136along communication line162dthat indicates to a system operator that identification of sample190was 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.

If a match between the sample absorption information and the reference information is not found by processor134, the processor can send an electronic signal to display136that indicates to the system operator that sample190was not successfully identified. The electronic signal can include, in some embodiments, a prompt to the system operator to repeat the sample absorption measurements.

Reference information stored in storage unit140can 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 sample190is successful, processor134can be configured to compare the identity of sample190against one or more lists of prohibited substances stored in storage unit140. If sample190appears on a list as a prohibited substance, processor134can alert the system operator that a prohibited substance has been detected. The alert can include a warning message displayed on display136and/or a colored region (e.g., a red-colored region) on display136. Processor134can also be configured to sound an audio alarm via a speaker to alert the system operator.

Storage unit140typically includes a re-writable persistent flash memory module. The memory module, which is removable from enclosure156, is configured to store a database that includes a library of infrared absorption information about various substances. Processor134can retrieve reference absorption information from storage unit140via a request transmitted on communication line162b. Storage unit140can also store device settings and other configuration information such as default operating parameters. Other storage media can also be included in storage unit140, including various types of re-writable and non-rewritable magnetic media, optical media, and electronic memory.

Measurement device100also includes communication interface142, which receives and transmits signals from/to processor134via communication line162c. Communication interface142includes a wireless transmitter/receiver unit that is configured to transmit signals from processor134to other devices, and to receive signals from other devices and communicate the received signals to processor134. Typically, for example, communication interface142permits processor134to communicate with other devices—including other measurement devices100and/or computer systems—via a wireless network that includes multiple devices connected to the network, and/or via a direct connection to another device. Processor134can 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.

Processor134communicates with a central computer system to update the database of reference information stored in storage unit140. Processor134is configured to periodically contact the central computer system to receive updated reference information, and processor134can 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.

Processor134can 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.

In some embodiments, measurement device100can 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 processor134to 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 device100.

Typically, input device138includes a control panel that enables a system operator to set configuration options and change operating parameters of measurement device100. In some embodiments, measurement device100can 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 device100by 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.

Radiation source102includes one or more laser diodes configured to provide infrared radiation, so that measurement device100functions as an infrared spectrometer. Typically, for example, the infrared radiation provided by source102includes a distribution of wavelengths, and a center wavelength of the distribution is about 785 nm. In general, radiation source102can 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 source102can 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).

In certain embodiments, the properties of radiation168provides by source102can be altered by control signals from processor134. For example, processor134can adjust an intensity and/or a spectral distribution of radiation168. Processor134can adjust spectral properties of radiation168by activating one or more filter elements (not shown inFIG. 1), for example. In general, measurement device100can include lenses, mirrors, beamsplitters, filters, and other optical elements that can be used to condition and adjust properties of radiation168.

Detector132is configured to measure reflected radiation beam176after the beam leaves prism122. Typically, detector132includes a pyroelectric detector element that generates an electronic signal, the magnitude of the signal being dependent on an intensity of radiation beam176. In general, however, detector132can include a variety of other detection elements. For example, in some embodiments, detector132can be a photoelectric detector (e.g., a photodiode) that generates an electronic signal with a magnitude that depends on the intensity of radiation beam176.

Radiation source144generates radiation beam178that is used to measure the position of mirror110. Radiation source144includes a vertical cavity surface-emitting laser (VCSEL) that generates radiation having a central wavelength of 850 nm. In general, radiation source144can include a variety of sources, including laser diodes, light-emitting diodes, and lasers. Radiation beam178can 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 beam178is 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).

Detector150can include a variety of different detection elements configured to generate an electronic signal in response to beam184. In some embodiments, for example, detector184includes a pyroelectric detector. In certain embodiments, detector184includes 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 beam184can be used in detector150.

As shown inFIG. 1, mirror110includes two opposite reflecting surfaces110aand110b. An enlarged schematic diagram of mirror110is shown inFIG. 2. Mirror110includes a substrate110c(formed of glass or fused silica, for example), with a first coating110ddisposed on substrate110cto form first reflecting surface110a, and a second coating110edisposed on an opposite surface of substrate110cto form second reflecting surface110e. Typically, beams172and180, which are incident on surfaces110aand110bof mirror110, respectively, have different central wavelengths. The materials that form first coating110dand second coating110eare selected to provide high reflectivity for beams172and180. In some embodiments, depending on the central wavelengths of beams172and180, a single coating material with high reflectivity at both central wavelengths is used to form coatings110dand110e. In certain embodiments, two different materials are used to form coatings110dand110e, where each coating material is selected to provide high reflectivity of beam172or beam180, as appropriate.

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, beams172and180reflect from a common surface of mirror110(e.g., surface110a). If beams172and180have central wavelengths that differ appreciably, then it is difficult to find a material for coating110dthat has very high reflectivity for both beams. As a result, one or even both of beams172and180is reduced in intensity due to reflection losses from mirror110.

Shaft112and bushing114permit smooth, vibration-decoupled motion of mirror110in a direction parallel to arrow164(e.g., in a direction parallel to the optical path of beam172). In the embodiment shown inFIG. 1, both shaft112and bushing114are substantially cylindrical, and bushing114has a central bore adapted to receive shaft112. In general, however, shaft112can be replaced by any member that is connected to mirror so that the member moves together with mirror110. Similarly, bushing114can, in general, include any sleeve or other member that is adapted to receive shaft112, and configured to permit motion of shaft112and mirror110relative to bushing114.

Shaft112and bushing114can generally be formed from the same material, or from different materials. Typically, shaft112and bushing114are formed from hard, smooth materials. Exemplary materials that can be used to form shaft112and/or bushing114include, but are not limited to, zirconia, aluminum oxide, silicon carbide, steel, and/or glass.

As discussed above, a fluid is disposed between shaft112and bushing114. Typically, the fluid is a viscous fluid that permits relatively friction-free movement of shaft112relative to bushing114. The fluid also decouples shaft112and bushing114, so that mechanical disturbances in one of these elements (e.g., bushing114) are not effectively transmitted to the other element (e.g., shaft112). The fluid therefore ensures that many of the optical elements—and mirror110in particular—of measurement device100are not significantly disturbed by mechanical perturbations. A variety of different fluids can be used between shaft112and bushing114including, for example, silicone oil.

The overall translation mechanism that is configured to translate mirror110includes shaft112, bushing114, and actuator116. Actuator116is coupled to shaft112and, on receiving suitable control signals from processor134, translates mirror110in a direction parallel to the optical path of beam172by applying a force to shaft112. Due to the applied force, shaft112moves relative to bushing114, causing translation of mirror110. Typically, actuator116includes 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 actuator116and bushing114(which can be formed from a metal and/or magnetic material, for example), causing translational motion of actuator116and coupled shaft112relative to bushing114. In general, many different types of actuators can be used to translate mirror110. Exemplary alternative actuators include voice coil actuators, stepper motors, flexure-based translation stages, and piezoelectric devices.

Measurement device100is generally configured to make multiple measurements of infrared absorption information from sample190to construct an interferogram. Typically, for example, each of the multiple measurements corresponds to a different position of mirror110along an axis parallel to the beam path of beam172. In certain embodiments, a maximum difference among the different positions of mirror110is 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).

As discussed above, during operation, prism122is placed in contact with sample190. Radiation is incident on surface122aof prism122that contacts sample190, and a portion of the incident radiation couples into sample190where it is absorbed. The remaining radiation undergoes total internal reflection from surface122aof prism122, and is detected by a suitable detector132. To contact sample190, prism122is positioned in an aperture than includes a protrusion166formed in a wall of enclosure156. Typically, protrusion166includes a liquid-proof seal to prevent sample fluid from entering enclosure156when prism122contacts a liquid sample190.

FIG. 3shows an enlarged schematic view of the aperture including protrusion166. Prism122includes a surface122athat is positioned to contact sample190. Radiation enters prism122through surface122b, and leaves prism122through surface122c. Surface122aincludes a coating206.

An edge of prism122opposite to surface122ais supported from below by a prism base204. Surface122aof prism122is also attached to mounting plate202to provide support to prism122from above. Support provided by plate202and base204allows prism122to withstand significant applied forces during operation without being displaced from its mounting position within protrusion166. During operation, a system operator can position measurement device100so that prism122(e.g., surface122a) contacts sample190, and the operator can apply a force to enclosure156so that prism122exerts a compressive force on sample190. This can improve a signal-to-noise ratio in measurements of reflected radiation beam176, and can enable measurement of certain samples which would otherwise yield inconclusive results in the absence of direct contact with prism122and/or the application of compressive force to sample190. Support base204and mounting plate202ensure that prism122remains in the same position within protrusion166during application of these forces.

Mounting plate202and support base204can be formed from the same or different materials. Typically, for example, mounting plate202and support base204include one or more metals. Exemplary materials from which either or both of mounting plate202and support base204can be formed include stainless steel and Hastelloy.

To withstand physical handling during measurement and chemical attack by samples, prism122is typically formed from a hard, chemically inert material. Prism122is also configured to provide for total internal reflection of radiation beam174, and so prism122is typically formed from a relatively high refractive index material. Materials that can be used to form prism122include naturally occurring and synthetic diamond, for example.

Protrusion166extends outward for a distance e from enclosure156. The extension of protrusion166permits contact between sample190and surface122aof prism122, and at the same time prevents contact between sample190and the rest of measurement device100. 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).

FIG. 4shows a plan view of the aperture that includes protrusion166. In the embodiment shown, surface122aof prism122has a substantially circular cross-sectional shape. In general, however, prism122can have a variety of different cross-sectional shapes, including ellipsoidal, rectangular, triangular, square, and irregular.

Returning toFIG. 3, due to the symmetric arrangement of beams174and176with respect to prism122, a total path length of the radiation in prism122is 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).

Prism122is positioned within protrusion166so that the exposed surface122aof prism122is substantially integral with an outer surface of measurement device100. In other words, prism122provides a window in the outer surface of measurement device100that permits incident radiation generated within the enclosure to interact with sample190. The positioning of prism122relative to enclosure156permits contact between prism122and sample190, and also ensures that the interior of enclosure156(e.g., the portion of enclosure156that includes the optical assembly) is not exposed to or contaminated by sample190.

Referring again toFIG. 1, prism122is mechanically isolated from the optical assembly mounted on assembly support152within enclosure156. Support base204and mounting plate202, each of which contacts prism122, are also mechanically decoupled from assembly support152and the optical elements mounted thereon. The mechanical isolation of prism122reduces coupling of mechanical perturbations into the optical assembly. For example, when prism122is placed in contact with sample190, mechanical vibrations can be induced in prism122due to the contact. If transmitted to the optical assembly, the vibrations could, for example, displace certain optical elements from alignment. By decoupling prism122and the optical assembly mounted on assembly support152, disruption of the alignment of the optical components of measurement device100is reduced or eliminated.

FIG. 5shows a simplified side cross-sectional view of measurement device100. Certain elements of measurement device100are not shown inFIG. 5for clarity. Assembly support152is mounted on support legs222, which are connected to an inner surface of hermetic enclosure224. Hermetic enclosure224encloses the optical assembly mounted on support152, and includes a window220that permits radiation beam174to leave hermetic enclosure224, and permits radiation beam176to enter hermetic enclosure224.

Hermetic enclosure224is hermetically sealed and mounted to enclosure156via posts226. The remaining interior portion of enclosure156, including protrusion166, includes a liquid-proof seal but not necessarily a hermetic seal. There are a number of advantages provided by the interior architecture of measurement device100. As discussed above, for example, prism122is mechanically decoupled from the optical assembly mounted to assembly support152, which prevents transmission of large-amplitude mechanical perturbations between prism122and support152(and the components thereon).

In addition, in some embodiments, a coating154can be disposed on one or more inner surfaces of enclosure156to further reduce the amplitude of any mechanical perturbations—in particular, those that arise from handling measurement device100- and to reduce or prevent transmission of perturbations to the elements of the optical assembly. Coating154can be formed from elastic materials such as silicone rubber, for example. In certain embodiments, a thickness of coating154is 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).

During use, the potential exists for the exposed surface (e.g., surface122a) of prism122to become contaminated with sample residues in such a way that surface122acannot be easily cleaned. In some cases, prism122can also become damaged (e.g., scratched) when prism122is used to apply pressure to samples. Contamination or damage to prism122may make it necessary to replace prism122by opening enclosure156. However, by providing a separate hermetically sealed enclosure224, exposure of the optical assembly mounted to assembly support152can be avoided, so that potential environmental contaminants and mechanical disturbances do not affect the optical components within hermetic enclosure224. Following replacement and/or cleaning of prism122, enclosure156can again be sealed with a liquid-proof seal; throughout the repair process, enclosure224remains hermetically sealed.

Enclosure156typically has a handheld form factor, so that measurement device100functions as a handheld infrared spectrometer, and in particular, as a handheld Fourier transform infrared spectrometer.FIG. 6shows a schematic diagram of enclosure156of measurement device100. In some embodiments, enclosure156can include regions of narrowed width232that are positioned and dimensioned to fit the hand of a system operator, to facilitate operation of device100as a handheld device. In certain embodiments, enclosure156can also include one or more shock-absorbing external protrusions230. The shock-absorbing external protrusions230can 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 enclosure156, and generally to protect the components of measurement device100.

Enclosure156can be formed from a variety of different materials. In some embodiments, enclosure156is formed from a hard, lightweight, durable material such as a hard plastic material. In certain embodiments, enclosure156can 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 enclosure156and the shock-absorbing external protrusions230together contribute to enclosure156being a rugged enclosure, configured to protect various elements positioned therein.

In some embodiments, enclosure156can also include a shoulder strap231, a portion of which is shown inFIG. 6. In addition or in the alternative to shoulder straps, enclosure156can include a variety of other features such as protruding handles, recessed handles, clips for attaching enclosure156to clothing or to other supports, and other devices that enhance the portability of enclosure156.

Referring again toFIG. 1, enclosure156has 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 enclosure156is less than 750 cm3(e.g., less than 600 cm3, less than 500 cm3, less than 400 cm3, less than 350 cm3, less than 300 cm3, less than 250 cm3, less than 200 cm3, less than 175 cm3, less than 150 cm3). In some embodiments, a total mass of measurement device100can 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).

In some embodiments, measurement device100can also include a support structure that is configured to connect to enclosure156and to support the enclosure during sample measurements.FIG. 7shows a schematic diagram of a support structure300that includes a base302and a mounting member304. Support structure300includes an attachment mechanism308positioned on mounting member304and configured to connect to enclosure156. Base302includes a stage310, and a depressed sample region312, configured to support a sample, is positioned in stage310in vertical alignment with protrusion166. Mounting member304permits translation of enclosure156in a direction indicated by arrow314(e.g., substantially perpendicular to a plane that includes stage310), so that prism122can be brought into contact with a sample positioned in sample region312. In some embodiments, sample region312can include alignment marks318that guide a system operator in the placement of a sample within sample region312to ensure good contact between the sample and an exposed surface of prism122.

Typically, support structure300is formed of a hard plastic material, for example, and structure300can be formed from the same material as enclosure156. In some embodiments, support structure can be formed from a material other than plastic, such as aluminum and/or stainless steel.

In certain embodiments, support structure300can be a portable support structure. For example, as shown inFIG. 7, base302and mounting member304are joined at hinge306. When not in use, support structure can be collapsed by folding mounting member304relative to base302, e.g., by rotating mounting member304relative to base302in the direction indicated by arrow316.

Support structure300can be used, for example, for effectively hands-free operation of measurement device100. By connecting enclosure156to mounting member304, both hands of a system operator are free to handle and position a sample190, for example. Measurement and identification of the sample can then be initiated with a press of a single key on input device138by the system operator.

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 prism122of the measuring device100and/or the application of compressive force to sample190. 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.

In some embodiments, a sample preparation device502can be configured to prepare samples of solid materials for analysis as well as to support an embodiment of measuring device100.FIG. 14Ashows the sample preparation device502placed on a flat surface510(e.g., a tabletop) and receiving and supporting an embodiment of the measuring device100.FIGS. 14B and 14Cshow views of a portion of the sample preparation device502(cross-section) and the measuring device100(side-view) in use together at different scales.FIG. 15andFIG. 16show the sample preparation device502and the measuring device100separately.

The sample preparation device502includes a protective boot512disposed around a housing514. The housing514includes an open end with a cavity540which is sized and configured to receive the end of measuring device100from which an optical interface122(e.g., a prism in the illustrated embodiment) extends. The housing514defines an aperture520extending through the housing514. The aperture520receives a sample dish516. In some embodiments, a seal554(e.g., an o-ring) limits the movement of material between the sample dish516and the housing514. In some cases, a lubricant (e.g., a silicon-based grease) is applied to the seal554.

A sample interface518is press-fit within a central aperture in the sample dish516. In some embodiments, an adhesive is used in addition to or as an alternative to the press-fit attachment of the sample interface518within the central aperture of the sample dish516. When the measuring device100is placed in the sample preparation device502, the sample interface518of the sample dish is aligned with the prism122of the measuring device100. The sample preparation device502also includes latches542configured to engage the measuring device100when the measuring device is inserted into sample preparation device502to crush and analyze a sample534of solid material (seeFIG. 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.

The sample dish516has a concave surface522extending laterally outward around the sample interface. The sample interface518extends axially upwards from the sample dish516When the sample preparation device is placed on a substantially horizontal surface for use, the outer edges of concave surface522extend upwards (e.g., farther from the flat surface510) farther than sample interface518. The sample interface518can 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 interface518contacts the concave surface522of the sample dish516. In the illustrated embodiment, the sample interface extends a distance d1(seeFIG. 14B) of approximately 0.55 mm from the point at which the sample interface518contacts the concave surface522of the sample dish516. In use, a small portion of the sample to be analyzed is placed on the sample interface518.

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 inFIGS. 14A and 14B. These terms do not imply any absolute orientation of the sample preparation device.

The sample interface518has a hardened surface (e.g., upper face524) which is resistant to scratches that might result from contact with prism122. In the illustrated embodiment, the sample interface518is formed of sapphire. In some embodiments, the sample interface518comprises (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 face524has 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.

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 device100into place in the sample preparation device502.

In some embodiments, a protective liner (not shown) is placed between the sample dish516/sample interface518and the measuring device100. The protective liner can be a thin disk (e.g., a plastic/Teflon®/Mylar® disk) whose shape generally conforms with the upper surface522of the sample dish516and the sample interface518. The protective liner can be disposable (e.g., replaceable after use with a certain number of samples).

The sample dish516has a first section526, adjacent the upper surface522, and a second section528, spaced apart from the upper surface522, with different outer dimensions. The first section526has a characteristic outer dimension which is smaller than the characteristic outer dimension of the second section528. In the illustrated example, the sample dish is substantially cylindrical in form and the first section526is a cylinder whose circumference is less than the circumference of the second section528. There is a sharp transition or step between the first section526and the second section528of the sample dish.

The aperture520has a first section530and a second section532which are, respectively, sized to slidably receive the first and second sections526,528of the sample dish516. The first section530of the aperture520is smaller than the second section532of the aperture520with a sharp transition or step between the first section530and the second section532of the aperture520. A resilient member536biases the sample dish516towards the first section530of the aperture520such that the step between sections526,528of the sample dish516engages the step between sections530,532of the aperture520in the absence of outside forces (e.g., in the absence of the measuring device100). The resilient member536can be, for example, a coil spring, a leaf spring, or a hydraulic cylinder. In the illustrated embodiment, the resilient member536is a coil spring which is located in the aperture520between the sample dish516and a retainer538(e.g., a cylindrical retainer with spiral threads on its outer surface). The resilient member536is selected to provide a force on, the sample dish and/or a specific pressure between the sample interface518and the prism122on the measuring device100when the measuring device100is pressed into the cavity540. 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.

In the illustrated embodiment, the housing514is inverted (e.g., placed with the cavity540downward) for installation of the sample dish516, the resilient member536, and the retainer538. The sample dish516is then placed in the aperture520with the first section526of the sample dish516oriented towards the first section530of the aperture520such that such that the step between sections526,528of the sample dish516rests on the step between sections530,532of the aperture520. The coil spring536is then placed in the aperture520with one end of the coil spring536resting on the sample dish516. The retainer538is pressed against the other end of the coil spring536to compress the coil spring536until the threads on the outer surface of the retainer538engage corresponding threads on the inner wall of the aperture520. The retainer538is then screwed into place.

After the sample dish516, the resilient member536, and the retainer538are installed in the housing514, the housing514is placed into protective boot512. The housing514can be held in place in the protective boot512by press-fit engagement between the housing514and the protective boot512. The protective boot512can provide a high-friction, slip resistant surface on the base of the sample preparation device502to help hold the sample preparation device502in place (e.g., when placed on a somewhat inclined surface). The presence of the protective boot512can prevent the retainer538from unscrewing from the housing514. The protective boot512can be removed from the housing514while the sample preparation device is being cleaned or when it is necessary to replace internal parts (e.g., the resilient member536) of the sample preparation device502. The protective boot512can be made of a durable, easy to clean material such as rubber.

The latches542of the sample preparation device502are mounted on housing514to pivot around a pin544. Resilient members546(e.g., coil springs) bias an upper end548of each latch542towards the cavity540defined by the housing514. When a user presses the measuring device100into the cavity540, contact with the measuring device100forces the upper ends548of latches542outward until the measuring device100is positioned to analyze a sample of solid material in the sample dish516. In this position, the upper ends548of the latches542engage latch hooks550on opposite sides of the measuring device100to latch the measuring device100into place. The user can release the measuring device100from the sample preparation device by pressing inward on the lower ends552of the latches542to rotate the upper ends548of the latches542out of engagement with the latch hooks550on the measuring device550.

The sample preparation device502is sized and configured to stably support the measuring device100when the measuring device100is snapped into place in the sample preparation device502. In the illustrated embodiment, the sample preparation device has a height h1of approximately 2.7 inches, a width w1of approximately 2.8 inches, and depth d2of approximately 2.3 inches and weighs approximately 1.4 pounds.

The embodiment of the measuring device100illustrated inFIG. 16has inner components substantially similar to the inner components of the measuring device100described with reference toFIGS. 1-5. The enclosure or housing156supports the electronic display136and the input device138which includes multiple keys for controlling operation of the measuring device100(e.g., menu driven operation using menus displayed on electronic display136). The presentation of graphical content (e.g., text and/or icons) on display136is controllable with at least a first mode in which text and/or icons being displayed are oriented with the relative top of the display136being the side of the display136towards the input device138and a second mode in which text and/or icons being displayed are oriented with the relative top of the display136being the side of the display136towards the prism122. During hand-held use (e.g., separate from sample preparation device502), it is typically easier for the user to read information displayed in the second mode. When the measuring device100is used with sample preparation device502, it is typically easier for the user to read information displayed in the first mode.

The measuring device100includes latch hooks550which are configured to engage the latches542when the measuring device100is inserted into the sample preparation device502. The measuring device100also includes features558extending laterally outward on each side of the prism122. The protruding features558on the measuring device100are configured to engage recesses556in the housing514of the sample preparation device502to align and guide the measuring device100into place when the measuring device100is inserted into the sample preparation device502.

The prism122has a contact face560with 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 prism122and an associated prism housing561extend outward from adjacent parts of the measuring device100. In the illustrated embodiment, the prism122is flush mounted within the prism housing561(i.e., the outer surfaces of the prism122and the prism housing are substantially co-planar). In the illustrated embodiment, the contact face560of the prism has an area of approximately 3.2 square millimeters. The prism122can 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 face560of the prism122.

The measuring device100is configured for handheld use. In the illustrated embodiment, the measuring device100has a height h2of approximately 8 inches, a width w2of approximately 4.5 inches, and depth d3of approximately 2 inches and weighs approximately 3 pounds. When the measuring device100is snapped into place in the sample preparation device502, the center of gravity of the combined unit remains above the bottom side562of the housing514until the combined unit is tilted more than about 15 degrees

In operation, a user sets the sample preparation device502on a substantially flat surface and places a small sample534of a solid material to be analyzed. The user then inserts the measuring device100into the sample preparation device502. Contact between protruding features558on the measuring device100and recesses556in the housing514of the sample preparation device502align and guide the measuring device100into place as the measuring device100is pressed downward. Contact with the measuring device100forces the upper ends548of latches542outward until the measuring device100is in position at which point the latches542engage the latch hooks550on the measuring device100.

As shown onFIG. 14C, during insertion, the sample534is compressed between the measuring device100and the sample preparation device502. In particular, the portion of the sample534located above the sample interface518is compressed between the prism122/prism housing561of the measuring device100and the sample interface518of the sample preparation device502. Excess portions of sample534squeezed out from between the prism122/prism housing561of the measuring device100and the sample interface518can fall into the sample dish516. The size of the sample534should be limited to reduce the likelihood that enough sample builds up in the sample dish516to bridge between the sample dish516and the measuring device as this could reduce the pressure between the prism122and the sample interface518.

The sample dish516and sample interface518can move axially downward as the measuring device100is inserted into the sample preparation device502. After the user releases the measuring device100and the measuring device100is being held in place by the latches542, the sample dish516and sample interface518have been displaced downward. Because of this displacement, the resilient member536exerts a force pressing the sample dish516and the sample interface518towards the prism. The amount of pressure applied to the sample between the sample interface518and the prism122is a function of the smaller of the area of the prism contact face/prism housing and the area of the upper face524of the sample interface518, the distance that the sample dish is displaced, and the characteristics of the resilient member536. For example, in the illustrated embodiment, the pressure applied to the portion of the sample between the can be estimated as
P=kd/a

whereP is pressure;d3is the distance that the sample dish516is displaced;k is the spring rate of the coil spring536; anda is the area of the upper face524of the sample interface518.
The resilient member536is selected to provide a specific pressure between the sample interface518and the prism122on the measuring device100when the measuring device100is pressed into the cavity540. For example, the resilient member536can be configured to apply between about 10 and 30 pounds of force when the measuring device100is inserted in the sample preparation device502. A pressure on a sample adjacent the prism122of 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 device502to provide higher pressures. However, increasing the pressures adjacent the prism122by increasing the spring force may make it difficult to insert the measuring device100into the sample preparation device. Increasing the pressures adjacent the prism122by decreasing the contact area (e.g., decreasing the size of the contact face560of the prism122and/or the upper face524of the sample interface518) may make it more likely that contact between the prism122and the sample interface518will damage one or both of these components.

After use, the sample preparation device502can 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.

The sample preparation device502can also be used to store the measuring device100when the measuring device100is not being used.

In the illustrated embodiment, the area a of the upper face524of the sample interface518, 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 face524of the sample interface518controls how much pressure develops between the sample interface518and the prism122. In the illustrated embodiment, the resilient member536is 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 spring536is assembled preloaded to deflect 0.33 inches. When inserted into the sample preparation device502, the measuring device100displaces the sample dish and additionally deflects the spring536a distance d3of approximately 0.09 inches. Other springs with lower or higher spring rates can be used.

When the measuring device100is inserted into the sample preparation device502, the pressure, P, on the sample adjacent the contact face560of the prism was calculated to be approximately 1,000 pounds per square inch. The illustrated embodiments of the measuring device100and the sample preparation device502have been used in combination to successfully analyze solid samples including fine to granular powders, flat sheets of plastic, flakes, beads, crystals, and rocks.

Although described for use with solid samples, the illustrated measuring device100and sample preparation device502could be used for analysis of liquid samples. However, in the absence of the particle size and distribution issues associated with solid samples, the measuring device100can be used to analyze liquid samples without the sample preparation device502by placing the prism122in the material to be analyzed if the material is present in a large volume (e.g., in a puddle). The measuring device100can 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 face560of the prism122.

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 device100can 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 device100and received via communication interface142.

Measurement device100is 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 device100reports a successful identification to a system operator. If the identities do not agree, measurement device100reports a failed identification. More generally, both the Raman scanning system and measurement device100can 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 device100can 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.

In certain embodiments, an infrared absorption spectrometer and a Raman spectrometer can be combined in a single handheld instrument.FIG. 8shows a schematic diagram of a measurement device400that 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 inFIG. 1. In addition to these components, measurement device400also includes a radiation source402, a beamsplitter404, a coupling window408, and a radiation analyzer406. Radiation source402and radiation analyzer406are in electrical communication with processor134via communication lines162jand162k.

As shown inFIG. 8, protrusion166—which includes prism122—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 prism122to determine infrared absorption information about the sample.

Coupling window408forms 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 window408to determine Raman scattering information about the sample. Radiation source402, after receiving a suitable control signal from processor134, generates incident radiation410. A portion of incident radiation410reflects from dichroic beamsplitter404and leaves enclosure156through coupling window408. Radiation410is incident on the sample, and a portion of the radiation is scattered by the sample as scattered radiation412. The scattered radiation (or a portion thereof) passes through dichroic beamsplitter404and enters radiation analyzer406. Once inside radiation analyzer406, reflected radiation412is manipulated (e.g., by dispersing scattered radiation412into 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 analyzer406can 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 analyzer406can also include various types of radiation detectors, and a processor.

The measured Raman scattering information is then transmitted to processor134. 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.

Typically, to perform a measurement on a sample, the sample is first positioned in proximity to coupling window408and Raman scattering information about the sample is measured. Then, measurement device400is re-oriented (or the sample is moved) so that the sample contacts the exposed surface of prism122, and infrared absorption information about the sample is measured. The Raman scattering and infrared absorption information is transmitted to processor134, and the processor identifies the sample based on the two types of information.

Processor134can 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, processor134can be configured to compare the Raman scattering information about the sample to a database of reference Raman scattering information stored in storage unit140for 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 interface142.

Similarly, processor134can compare the sample infrared absorption information to reference infrared absorption information stored in storage unit140to 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.

Processor134then compares the substances matched by the sample Raman scattering information and infrared absorption information. If the matched substances are the same for each, processor134outputs a signal to display136that 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.

Returning toFIG. 1, in some embodiments, measurement device100can include only an infrared scanning subsystem (e.g., no Raman scanning system), and processor134can 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 device100. Measurement device100can be configured to receive the sample Raman scattering information via communication interface142, and to compare the sample Raman scattering information to reference Raman scattering information stored in storage unit140to determine an identity of the sample. Measurement device100can 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.

In certain embodiments, processor134can 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, processor134can 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.

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−1. This broad band can obscure other spectral features which could otherwise be used to identify the sample. Therefore, in some embodiments, processor134can 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 9Bshow 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 processor134to circumvent a number of troublesome infrared spectral features, including —OH stretching bands as disclosed above.

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. Processor134can 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 10Bshow 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−1that can be used to identify the sample. In general, the use of Raman scattering information can be reduced relative to infrared absorption information by processor134to circumvent a number of troublesome Raman spectral features, including fluorescence bands as disclosed above.

In some embodiments, both Raman scattering information and infrared absorption information can be used to identify a sample in complementary fashion.FIGS. 11A and 11Bshow 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 processor134to determine an identity of the sample.

Referring again toFIG. 8, radiation source402can include one or more of a variety of sources including, for example, laser diode sources, light-emitting diode sources, and laser sources. Incident radiation410provided by source402generally 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 radiation410with a center wavelength less than 450 nm.

The intensity of incident radiation410can generally be selected as desired to generate a Raman scattering signal from the sample. Typically, the intensity of incident radiation410can be tens or hundreds of milliwatts, for example. However, in certain embodiments (such as, for example, embodiments where a center wavelength of incident radiation410is less than 450 nm), an intensity of incident radiation410can 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 radiation410.

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 prism122. 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. 12shows a measurement device500where incident radiation from each of the infrared and Raman scanning subsystems passes into prism122and is incident on sample190. Many of the components inFIG. 12have been previously discussed. Source402generates incident radiation beam410that is directed by mirror420to enter prism122and interact with the sample via surface122a. Scattered radiation beam412is directed by mirror422to enter radiation analyzer406. Radiation analyzer406disperses wavelength components of scattered radiation beam412and measures the dispersed components to determine Raman scattering information about the sample.

In the embodiment shown inFIG. 12, both the infrared scanning subsystem and the Raman scanning subsystem direct incident light to a common location on sample190. In addition to reducing noise due to spatial inhomogeneity in the measured sample information, the configuration of measurement device500shown inFIG. 12is simpler than the configuration of measurement device400inFIG. 8, requiring fewer apertures. Further, measurements of both Raman scattering information and infrared absorption from the sample can be made without re-positioning measurement device500relative to sample190.

Although the embodiment shown inFIG. 12is primarily configured to analyze samples190in contact with prism122, Raman scanning subsystems can be used to analyze samples that are spaced apart from the prism122. 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 13Bshow portions of an optical analysis device600that is generally similar to the optical analysis device500shown inFIG. 12except for the configuration of the Raman analysis subsystem.

In optical analysis device600, source402generates incident radiation beam410that is directed by a Raman optical assembly. With this construction, the output of excitation light source402is collimated through lens615. A bandpass filter620(or combination of multiple bandpass filters620A,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 filter625, which in this configuration may be a laser line reflector (at a 40 degree Angle of Optical Incidence, AOI) and a filter630(at a 5 degree AOI), and then it is focused through lens635to excite specimen190. Although specific AOI values are described for this illustrative example, the AOI values may vary from one embodiment to another. In one embodiment, filter630can be a long-pass filter. In this embodiment, laser line reflector625can 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 lens635and passed through filter630. Alternatively, the Raman signal may pass through multiple filters (e.g., in addition to passing through filter630, the Raman signal may pass through additional filter645, at a 5 degree AOI). In one embodiment, additional filter645is also a long-pass filter. When the Raman signal from the specimen is passed though filter630, filter630can also serve to block the laser line. Filters630and645can provide up to >OD10 filtration of the laser line before the light is redirected through broadband reflector650(at a 45 degree AOI) and focus lens655into radiation analyzer406. 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 prism122is truncated such that incident radiation beam410passes through a flat face122dwhich is substantially parallel to the exterior surface122aof the prism.

The lens635has a focal length1. A translation mechanism (not shown) can be operated to move the lens635parallel to the optical axis of the lens635. In a first position (see FIG.13A), the lens635focuses incident radiation beam410at point co-located with the exterior surface122aof the prism122. 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 analyzer406. In a second position (seeFIG. 13B), the lens635is moved towards the prism such that the lens635focuses incident radiation beam410at point past the exterior surface122aof the prism122. In this position, the Raman subsystem can be used to analyze samples190that are spaced apart from optical analysis device600.

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.

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.

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.

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.

Other embodiments are in the claims.