US20110208462A1 - System and method for instrument correction using transmission efficiency - Google Patents
System and method for instrument correction using transmission efficiency Download PDFInfo
- Publication number
- US20110208462A1 US20110208462A1 US12/931,836 US93183611A US2011208462A1 US 20110208462 A1 US20110208462 A1 US 20110208462A1 US 93183611 A US93183611 A US 93183611A US 2011208462 A1 US2011208462 A1 US 2011208462A1
- Authority
- US
- United States
- Prior art keywords
- test data
- operating point
- filter
- interacted photons
- instrument response
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 238000000034 method Methods 0.000 title claims abstract description 58
- 238000012937 correction Methods 0.000 title claims abstract description 45
- 230000005540 biological transmission Effects 0.000 title abstract description 42
- 238000012360 testing method Methods 0.000 claims abstract description 74
- 230000004044 response Effects 0.000 claims abstract description 64
- 238000005286 illumination Methods 0.000 claims abstract description 17
- 230000007613 environmental effect Effects 0.000 claims abstract description 12
- 239000000523 sample Substances 0.000 claims description 45
- 239000004973 liquid crystal related substance Substances 0.000 claims description 32
- 238000001069 Raman spectroscopy Methods 0.000 claims description 22
- 239000013074 reference sample Substances 0.000 claims description 19
- 230000003287 optical effect Effects 0.000 claims description 14
- 238000013500 data storage Methods 0.000 claims description 7
- 238000001228 spectrum Methods 0.000 description 58
- 238000005259 measurement Methods 0.000 description 24
- 238000000701 chemical imaging Methods 0.000 description 16
- 238000003384 imaging method Methods 0.000 description 16
- 230000003595 spectral effect Effects 0.000 description 13
- 238000005516 engineering process Methods 0.000 description 11
- 230000006870 function Effects 0.000 description 8
- 229910000530 Gallium indium arsenide Inorganic materials 0.000 description 6
- 238000004458 analytical method Methods 0.000 description 6
- 239000000835 fiber Substances 0.000 description 6
- 238000013459 approach Methods 0.000 description 5
- 230000000873 masking effect Effects 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 238000003332 Raman imaging Methods 0.000 description 4
- 238000004891 communication Methods 0.000 description 4
- 238000001514 detection method Methods 0.000 description 4
- 238000011156 evaluation Methods 0.000 description 4
- 239000005262 ferroelectric liquid crystals (FLCs) Substances 0.000 description 4
- 238000012986 modification Methods 0.000 description 4
- 230000004048 modification Effects 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 238000002834 transmittance Methods 0.000 description 4
- 238000002329 infrared spectrum Methods 0.000 description 3
- 230000010287 polarization Effects 0.000 description 3
- VLJQDHDVZJXNQL-UHFFFAOYSA-N 4-methyl-n-(oxomethylidene)benzenesulfonamide Chemical compound CC1=CC=C(S(=O)(=O)N=C=O)C=C1 VLJQDHDVZJXNQL-UHFFFAOYSA-N 0.000 description 2
- 101000694017 Homo sapiens Sodium channel protein type 5 subunit alpha Proteins 0.000 description 2
- 238000001237 Raman spectrum Methods 0.000 description 2
- 239000012472 biological sample Substances 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 239000003153 chemical reaction reagent Substances 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- WPYVAWXEWQSOGY-UHFFFAOYSA-N indium antimonide Chemical compound [Sb]#[In] WPYVAWXEWQSOGY-UHFFFAOYSA-N 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 230000007246 mechanism Effects 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 229910021340 platinum monosilicide Inorganic materials 0.000 description 2
- 230000005855 radiation Effects 0.000 description 2
- 238000004611 spectroscopical analysis Methods 0.000 description 2
- 238000004566 IR spectroscopy Methods 0.000 description 1
- 238000003841 Raman measurement Methods 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- KXNLCSXBJCPWGL-UHFFFAOYSA-N [Ga].[As].[In] Chemical compound [Ga].[As].[In] KXNLCSXBJCPWGL-UHFFFAOYSA-N 0.000 description 1
- 230000003044 adaptive effect Effects 0.000 description 1
- 230000003190 augmentative effect Effects 0.000 description 1
- 230000006399 behavior Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000010219 correlation analysis Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000005284 excitation Effects 0.000 description 1
- 239000002360 explosive Substances 0.000 description 1
- 231100001261 hazardous Toxicity 0.000 description 1
- 238000003331 infrared imaging Methods 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 238000003064 k means clustering Methods 0.000 description 1
- 238000010905 molecular spectroscopy Methods 0.000 description 1
- 238000012634 optical imaging Methods 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 239000011368 organic material Substances 0.000 description 1
- 238000010239 partial least squares discriminant analysis Methods 0.000 description 1
- 238000010238 partial least squares regression Methods 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 238000005424 photoluminescence Methods 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 238000000513 principal component analysis Methods 0.000 description 1
- 108090000623 proteins and genes Proteins 0.000 description 1
- 239000012925 reference material Substances 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 239000011343 solid material Substances 0.000 description 1
- 238000012306 spectroscopic technique Methods 0.000 description 1
- 238000010183 spectrum analysis Methods 0.000 description 1
- 239000010421 standard material Substances 0.000 description 1
- 238000000411 transmission spectrum Methods 0.000 description 1
- 238000010200 validation analysis Methods 0.000 description 1
Images
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
- G01J3/02—Details
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
- G01J3/02—Details
- G01J3/0297—Constructional arrangements for removing other types of optical noise or for performing calibration
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
- G01J3/28—Investigating the spectrum
- G01J3/44—Raman spectrometry; Scattering spectrometry ; Fluorescence spectrometry
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/27—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands using photo-electric detection ; circuits for computing concentration
- G01N21/274—Calibration, base line adjustment, drift correction
- G01N21/276—Calibration, base line adjustment, drift correction with alternation of sample and standard in optical path
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
- G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
- G01N21/65—Raman scattering
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2201/00—Features of devices classified in G01N21/00
- G01N2201/12—Circuits of general importance; Signal processing
- G01N2201/129—Using chemometrical methods
- G01N2201/1293—Using chemometrical methods resolving multicomponent spectra
Definitions
- SWIR Short-Wavelength Infrared Multi-Conjugate Liquid Crystal Tunable Filter
- No. 61/434,034 filed on Jan. 19, 2011, entitled “VIS-SNIR Multi-Conjugate Tunable Filter,” No. 61/460,816, filed on Jan. 7, 2011, entitled “Conformal Filter and Method for Use Thereof,” and No. 61/403,141, filed on Sep. 10, 2010, entitled “Systems and Methods for Improving Imaging Technology.”
- Spectroscopic imaging combines digital imaging and molecular spectroscopy techniques, which can include Raman scattering, fluorescence, photoluminescence, ultraviolet, visible and infrared absorption spectroscopies. When applied to the chemical analysis of materials, spectroscopic imaging is commonly referred to as chemical imaging. Instruments for performing spectroscopic (i.e. chemical) imaging typically comprise an illumination source, image gathering optics, focal plane array imaging detectors and imaging spectrometers.
- the sample size determines the choice of image gathering optic.
- a microscope is typically employed for the analysis of sub micron to millimeter spatial dimension samples.
- macro lens optics are appropriate.
- flexible fiberscope or rigid borescopes can be employed.
- telescopes are appropriate image gathering optics.
- FPA detectors For detection of images formed by the various optical systems, two-dimensional, imaging focal plane array (“FPA”) detectors are typically employed.
- the choice of FPA detector is governed by the spectroscopic technique employed to characterize the sample of interest.
- silicon (“Si”) charge-coupled device (“CCD”) detectors or CMOS detectors are typically employed with visible wavelength fluorescence and Raman spectroscopic imaging systems
- indium gallium arsenide (“InGaAs”) FPA detectors are typically employed with near-infrared spectroscopic imaging systems.
- Wide-field spectroscopic imaging of a sample can be implemented by collecting spectra over the entire area encompassing the sample simultaneously using an electronically tunable optical imaging filter such as an acousto-optic tunable filter (“AOTF”) or a liquid crystal tunable filter (“LCTF”).
- AOTF acousto-optic tunable filter
- LCTF liquid crystal tunable filter
- the organic material in such optical filters are actively aligned by applied voltages to produce the desired bandpass and transmission function.
- the spectra obtained for each pixel of such an image thereby forms a complex data set referred to as a hyperspectral image which contains the intensity values at numerous wavelengths or the wavelength dependence of each pixel element in this image.
- UV Ultraviolet
- VIS visible
- NIR near infrared
- SWIR short-wave infrared
- MIR mid infrared
- LWIR long wave infrared wavelengths
- the real physical phenomenon being measured is the Raman scattered light emanating from a location in a field-of-view represented by a pixel in a data set.
- the Raman scattered light passes through a set of imaging optics to a detector.
- the optics are fixed components made of solid materials with stable optical characteristics.
- one of the optics is a liquid crystal tunable filter spectroscopic imaging element. This is a dynamically tunable narrow bandpass ( ⁇ 0.25 nm FWHM) filter that allows imaging of the same field-of-view at different wavelengths, without moving any optics.
- a disadvantage of this device is that there can be fluctuations in the transmission efficiency that depend on characteristics such as temperature, atmospheric pressure and humidity. These fluctuations are significantly larger than fluctuations of properties of standard physical optics in the same conditions and manifest themselves in the amount of light that is transmitted, and hence on the amount of Raman scattered light that is recorded at the detector. Because these fluctuations vary with environmental conditions, they manifest themselves differently at different operating conditions.
- the present disclosure relates to a system and method for correcting instrument response of an optical instrument. More specifically, the present disclosure relates to a system and method for correcting instrument response using an independent system with a known calibration.
- FIG. 1A is illustrative of the wavelength to wavelength variation in transmission of a tunable filter.
- FIG. 1B is illustrative of the variance that occurs in filter transmission over time.
- FIG. 2 is representative of a method of the present disclosure.
- FIG. 3A illustrates an image and associated spectra for regions of a sample.
- FIG. 3B illustrates the same field of view as FIG. 3A after masking for pixels sampled by a dispersive spectrometer.
- FIG. 4 is illustrative of a system of the present disclosure.
- FIG. 5 is representative of a method of the present disclosure.
- FIG. 6 is illustrative of a system of the present disclosure.
- FIG. 7A is a data chart representative of an exemplary MCF SWIR filter's transmittance performance with respect to the temperature increment.
- FIG. 7B is a plot representative of an exemplary MCF SWIR filter's transmittance performance with respect to the temperature increment.
- FIG. 8A is a data chart representative of an exemplary MCF Raman filter's transmittance performance with respect to the temperature increment.
- FIG. 8B is a plot representative of an exemplary MCF Raman filter's transmittance performance with respect to the temperature increment.
- the present disclosure provides for a system and method which hold potential for enabling the evaluation of an imperfect optical component or system in terms of its transmission or detection performance.
- the present disclosure contemplates that any deviations from the perfect or ideal performance may be measured and accounted for.
- the spectrum would be a flat horizontal line as a function of wavelength.
- an ideal light source that produces the same number of photons at each wavelength may be used.
- the measured spectrum is not a straight line.
- the real spectrum obtained from a perfect source with the same number of photons at each wavelength carries information about the instrument response of the real-world, imperfect optical instrument.
- the instrument response is the spectral response. In general, instrument response as a function of any number of parameters can be measured and corrected for.
- the presence of the instrument response i.e., a manifestation of an instrument's imperfections or deviations from the ideal response—is evident in both dispersive and imaging spectroscopy experiments.
- a dispersive spectroscopy measurement e.g., measurement of a Raman spectrum
- the baseline on which the Raman spectrum sits is not a flat line.
- the features in the baseline e.g., its lack of ideal flatness
- Raman molecular imaging may be one technology which holds potential for delivering this molecular information into the context of histopathological evaluation of tissue samples.
- RMI builds on the demonstrated success of Raman spectroscopy in the analysis of biological samples by integrating full field-of-view digital imaging with high precision spectrally sensitive optics.
- the system and method of the present disclosure hold potential for optimizing the instrumentation so that it can perform in a stable reproducible fashion to deliver this biological information to the clinicians on a routine basis.
- infrared imaging may hold similar potential for application in these scenarios.
- FIGS. 1A and 1B show a plot of this response with the mean intensity of an image of a piece of this material as a function of Raman shift acquired with a tunable filter-based system.
- FIG. 1A is illustrative of the wavelength to wavelength variation in the transmission of the tunable filter with the known spectrum of the material (red dashed line). A single frame of the image stack is shown to indicate the level of pixel to pixel to noise.
- FIG. 1B is illustrative of the detailed spectrum of the same measurement made on the same sample at a different time to indicate the variance that occurs in the filter transmission over time.
- the Raman image is acquired over the full Raman scattering spectral range.
- the image is comprised of a series of 196 frames acquired at different center bandpass settings of the filter.
- the plot represented in red dashed line is the known spectrum of the material provided by NIST.
- the red solid line is the intensity of each frame versus center band setpoint.
- the mean plus and minus the standard deviation of each frame is shown the mean plus and minus the standard deviation of each frame (blue dotted lines). This is included to point out that the variance from frame to frame is not due to the pixel noise of the image (which is indicated by the standard deviations).
- the transmission spectrum is not smooth; it has sharp discontinuities and could not be well approximated by an analytic equation.
- the fundamental reason why these discontinuities exist is related to the operation of liquid crystal tunable filters as a collection of independently functioning liquid crystal elements stacked together.
- the tunable filter works by aligning the center bandpass of a series of liquid crystal elements which can each be independently adjusted in terms of a periodic (as a function of wavelength) transmission function.
- the overall bandpass of the filter is determined by the multiplication of the transmission of each of the elements.
- an operating point is chosen for each element of the filter.
- the filter performance is optimized around high center bandpass throughput and high out-of-band light rejection. In order to perform this optimization, operating point choices are made that can lead to very different operating points for a given element at two adjacent wavelength setpoints. Because the choices of operating points are driven by out-of-band rejection, transmission smoothness is sacrificed. This is true about filters from multiple vendors with different designs.
- FIG. 1B illustrates the mean and standard deviation spectra for a second measurement on the same instrument.
- the assumption here is that of all of the components in the system, the tunable filter is the least stable in terms of behavior over time. This assumption is supported by the clear presence of discontinuities consistent with filter reset points in the spectra shown and the fact that all of the other fixed optics in the system have smooth transmission functions over the relevant wavelength range.
- IRC instrument response correction
- ⁇ IRC is a unitless scalar that is essentially the transmission efficiency of the system at the wavelength being studied. Actual measurements are made in the units of output of the CCD camera. For the purposes of the relationship above, the unit conversions are ignored because they do not impact the instrument response correction and R Meas and R true should be considered to include such unit conversions that are necessary to move them both into the unit of detector counts.
- the present disclosure provides for a method incorporating the use of the SRM2242 from NIST. Based on the instructions for use the method involves: placing the standard sample in a Raman measurement system, measuring a spectrum of the material on the instrument, calculating an instrument response correction based on the known spectrum and the measured spectrum, using the instrument response correction spectrum to correct subsequent measurements on the system.
- This method may hold potential for systems which have a dispersing element and either a linear CCD detector, or some method of scanning the dispersing element as in a scanning monochromator.
- a dispersing element and either a linear CCD detector, or some method of scanning the dispersing element as in a scanning monochromator.
- the same basic approach may be taken where the measured spectrum is the spectrum at either a single pixel or the mean of spectra acquired at many pixels.
- Experimental measurements using this methodology may use the available NIST standard as a sample and existing equipment using Raman imaging systems integrating fixed optics and tunable filters from different manufacturers can be surveyed.
- the present disclosure provides for a system and method for determining an instrument response correction by making a second measurement on the sample with an independent measurement system with established calibration.
- Dispersing spectrometers are built of fixed optical components with well understood drift and fluctuation due to environmental changes. Because of this established validation a dispersing spectrometer can be used as a plausible reference measurement used to correct measurements made with other devices.
- the present disclosure contemplates the use of an independent measurement of the sample using a dispersing spectrometer as the true spectrum of the sample as the known reference value.
- FIG. 2 illustrates one embodiment of the present disclosure.
- the method, 200 provides or illuminating a sample in step 210 to thereby generate a first plurality of interacted photons and a second plurality of interacted photons.
- This illumination may be achieved by utilizing at least one of active illumination and passive illumination.
- the illumination may be achieved using a laser light source.
- passive illumination the illumination may be achieved using a solar radiation source.
- At least one of the first and second pluralities of interacted photons may comprise photons scattered by the sample, reflected by the sample, absorbed by the sample, emitted by the sample, and combinations thereof.
- the sample may be a biological sample.
- the sample may comprise a chemical sample, an explosive sample, a hazardous sample, a forensic sample, a pharmaceutical sample, and combinations thereof.
- a first plurality of interacted photons may be detected using a dispersive spectrometer in step 220 to thereby generate at least one reference spectrum representative of said sample.
- these photons may be transmitted to a dispersive spectrometer via a fiber optic.
- this fiber optic may comprise a fiber array spectral translator device.
- This reference spectrum may comprise a Raman reference spectrum, an infrared reference spectrum, and combinations thereof.
- An infrared spectrum as contemplated by the present disclosure, may comprise at least one of: a short-wave infrared reference spectrum, a near infrared reference spectrum, a mid-wave infrared spectrum, a long wave infrared spectrum, and combinations thereof.
- multiple reference spectra representative of said sample may be obtained using a dispersive spectrometer. These reference spectra may then be assessed to determine a mean reference spectrum.
- a second plurality of interacted photons may be passed through a tunable filter.
- this tunable filter may sequentially filter the second plurality of interacted photons into a plurality of predetermined wavelength bands.
- the tunable filter may comprise technology available from ChemImage Corporation, Pittsburgh, Pa. This technology is more fully described in the following U.S. Patents and U.S. patent applications, which are hereby incorporated by reference in their entireties: U.S. Pat. No. 6,992,809, issued on Jan. 31, 2006, entitled “Multi-Conjugate Liquid Crystal Tunable Filter”; U.S. Pat. No. 7,362,489, issued on Apr.
- Multi-Conjugate Liquid Crystal Tunable Filter U.S. Provisional Patent Application No. 61/324,963, filed on Apr. 16, 2010, entitled “Short-Wavelength Infrared (SWIR) Multi-Conjugate Liquid Crystal Tunable Filter”; U.S. Provisional Patent Application No. 61/460,816, filed on Jan. 7, 2011, entitled “Conformal Filter and Method for Use Thereof”; and U.S. Provisional Patent Application No. 61/403,141, filed on Sep. 10, 2010, entitled “Systems and Methods for Improving Imaging Technology.”
- SWIR Short-Wavelength Infrared
- the tunable filter may comprise a liquid crystal tunable filter, a multi-conjugate liquid-crystal tunable filter, and combinations thereof.
- Other embodiments of the present disclosure may utilize a device selected from the group consisting of: an acousto-optical tunable filter (“AOTF”), Evans Split-Element liquid crystal tunable filter, Solc liquid crystal tunable filter, Ferroelectric liquid crystal tunable filter, Fabry Perot liquid crystal tunable filter, a hybrid filter, and combinations thereof.
- AOTF acousto-optical tunable filter
- Evans Split-Element liquid crystal tunable filter Evans Split-Element liquid crystal tunable filter
- Solc liquid crystal tunable filter Solc liquid crystal tunable filter
- Ferroelectric liquid crystal tunable filter Ferroelectric liquid crystal tunable filter
- Fabry Perot liquid crystal tunable filter Fabry Perot liquid crystal tunable filter
- the method 200 provides for detecting a second plurality of interacted photons in step 240 .
- This detection 240 may be accomplished using an imaging detector and generate at least one hyperspectral test image representative of the sample.
- this hyperspectral test image may comprise at least one of: a Raman hyperspectral image, an infrared hyperspectral image, and combinations thereof.
- This infrared hyperspectral image may be selected from the group consisting of: a short-wave infrared hyperspectral image, a near infrared hyperspectral image, a mid-wave infrared hyperspectral image, a long-wave infrared hyperspectral image, and combinations thereof.
- the method 200 may detect said first and second plurality of photons substantially simultaneously. This embodiment holds potential for providing active feedback during operation. In another embodiment, the method 200 may detect said first and second plurality of photons sequentially.
- a hyperspectral test image may be assessed to thereby determine a mean test spectrum.
- This mean test spectrum may be representative of the mean intensity of a plurality of pixels in said hyperspectral test image.
- the mean test spectrum may be compared to a reference spectrum in step 260 to determine an instrument response correction. This comparison may be achieved by applying one or more chemometric techniques. Such techniques may include, but are not limited to, the following: principal component analysis (“PCA”), multivariate curve resolution (“MCR”), partial least squares discriminant analysis (“PLSDA”), k means clustering, band t.
- PCA principal component analysis
- MCR multivariate curve resolution
- PLSDA partial least squares discriminant analysis
- k means clustering, band t.
- spectral unmixing algorithm entropy method, adaptive subspace detector, cosine correlation analysis (“CCA”), Euclidian distance analysis (“EDA”), partial least squares regression (“PLSR”), spectral mixture resolution (“SMR”), a spectral angle mapper metric, a spectral information divergence metric, a Mahalanobis distance metric, a spectral unmixing algorithm, and combinations thereof.
- CCA cosine correlation analysis
- EDA Euclidian distance analysis
- PLSR partial least squares regression
- SMR spectral mixture resolution
- a spectral unmixing metric is disclosed in U.S. Pat. No. 7,072,770 entitled “Method for Identifying Components of a Mixture via Spectral Analysis,” which is hereby incorporated by reference in its entirety.
- an instrument response correction may be applied to said hyperspectral test image.
- Application of an instrument response correction 270 may result in an adjusted mean test spectrum associated with the test image.
- This adjusted mean test spectrum may be substantially equal to the reference spectrum obtained in step 220 .
- the method 200 may further comprise masking a hyperspectral test image.
- the mask may be such as to include those pixels sampled by said dispersive spectrometer and exclude those pixels not sampled by said dispersive spectrometer.
- the base assumption is that the mean spectrum of the imaged area measured from a dispersive spectrometer should match the mean spectrum from the image acquired of the same area through the tunable filter.
- This type of measurement is feasible because the tunable filter only uses one polarization of the light emanating from the sample. Light with the unused polarization can be sent to a dispersing spectrometer and simultaneously measured to provide the reference spectrum. Key considerations relevant to this approach are: 1) to ensure that light collected with each polarization will have the same spectral distribution, 2) to ensure that spatial sampling and detection efficiency are matched for both arms of the measurement system, 3) to ensure that any sample changes during the course of the image based measurement are captured in the parallel dispersive spectrometer based measurement.
- FIGS. 3A and 3B illustrate both a typical mask of where fibers sample a field of view of a microscope and the variation in spectral of some localized components of tissue which photobleach or photodegrade during the image acquisition.
- FIG. 3A illustrates an image and spectra from a Raman image of tissue. The spectra shown are from the two locations in the image indicating typical tissue signature 310 and localized fluorescent object 320 .
- FIG. 3B illustrates the same field of view after masking for the pixels sampled by a dispersive spectrometer. The spectra shown are the mean spectrum of the image before 330 and after 340 the masking.
- the present disclosure also provides for a system, illustrated by FIG. 4 .
- the system 400 may comprise an illumination source 410 configured to illuminate a sample 420 to thereby generate a first plurality of interacted photons and a second plurality of interacted photons.
- the system may comprise a platform for holding the sample.
- These interacted photons may be collected using collection optics 430 .
- a first plurality of interacted photons may be transmitted to a dispersive spectrometer 450 via a fiber optic 440 , which may comprise a fiber array spectral translator device (“FAST”).
- FAST technology may comprise technology available from ChemImage Corporation, Pittsburgh, Pa.
- a second plurality of interacted photons may be passed through a tunable filter 460 .
- This tunable filter 460 may comprise a liquid crystal tunable filter, a multi-conjugate liquid crystal tunable filter, and combinations thereof.
- the tunable filter 460 may also comprise an acousto-optical tunable filter (“AOTF”), Evans Split-Element liquid crystal tunable filter, Solc liquid crystal tunable filter, Ferroelectric liquid crystal tunable filter, Fabry Perot liquid crystal tunable filter, a hybrid filter, and combinations thereof.
- the tunable filter 460 may be configured so as to sequentially filter interacted photons into a plurality of predetermined wavelength bands.
- An imaging detector 470 may be configured so as to detect a second plurality of interacted photons and generate at least one hyperspectral test image.
- An imaging detector 470 may comprise a Raman hyperspectral imaging detector, an infrared hyperspectral imaging detector, and combinations thereof.
- An infrared hyperspectral imaging detector may comprise at least one of: a short-wave infrared hyperspectral imaging detector, a near infrared hyperspectral imaging detector, a mid-wave infrared hyperspectral imaging detector, a long wave hyperspectral imaging detector, and combinations thereof.
- Imaging detector 470 may comprise a detector selected from the group consisting of: a CCD detector, an ICCD detector, an InGaAs detector, an extended range InGaAs detector, an InSb detector, a PtSi detector, a CMOS detector, a MCT detector, an intervac-intensified detector, a microbolometer, and combinations thereof.
- the system 400 may also be configured to operate in conjunction with one or more processors.
- this processor may be configured so as to generate a mean spectrum representative of a hyperspectral test image, compare a mean spectrum to a reference spectrum, determine an instrument response correction, and apply an instrument response correction to a hyperspectral image.
- the present disclosure also provides for a data storage medium containing program code, which when executed by a processor causes the processor to: illuminate a sample to generate a first plurality of interacted photons and a second plurality of interacted photons, detect a first plurality of interacted photons using a dispersive spectrometer to thereby generate a reference spectrum representative of a sample, pass a second plurality of interacted photons through a tunable filter, detect a second plurality of interacted photons using an imaging detector to thereby generate at least one hyperspectral test image, assess said hyperspectral test image to thereby determine a mean test spectrum wherein said mean test spectrum is representative of the mean intensity at each pixel in said hyperspectral test image, compare said mean test spectrum to a reference spectrum to thereby determine an instrument response correction, and apply said instrument response correction to said hyperspectral test image.
- program code when executed by a processor causes the processor to: illuminate a sample to generate a first plurality of interacted photons and a second plurality
- the data storage medium when executed by a processor may further cause the processor to obtain a plurality of reference spectra representative of a sample via said dispersive spectrometer and assess said plurality of reference spectra to thereby determine a mean reference spectrum representative of the sample.
- the processor may further mask a hyperspectral test image so as to include a first plurality of pixels sampled by said dispersive spectrometer and exclude a second plurality of pixels not sampled by said dispersive spectrometer.
- the present discourse also provides for a method for correcting for instrument response by having the instrument actively report its current status and correct the data during acquisition. This is possible in the case where a user has access to fundamental data acquired during the manufacturing of the filter and the ability to use that information during operation of a filter. Such interaction holds potential for enabling modification to the communication to and from the filter in a way that holds potential for instrument response correction.
- a filter control system may use a lookup table stored in memory to determine the proper set of control voltages for the stages that comprise the filter. This table may comprise a set of voltages for each possible bandpass center setpoint and operating temperature.
- the controller may query the temperature of the filter, refer to the lookup table to determine the appropriate control voltages for the temperature and center bandpass, then apply the appropriate voltage to each stage of the filter. To implement this method the controller may be modified to report the estimated transmission of the filter for the center bandpass and operating temperature.
- the present disclosure compensates a system and method to correct for variations in filter transmission.
- this variation can be corrected at the filter controller level by changing the code in the filter controller software to read and report appropriate transmission values from an augmented data lookup table. This may also involve a change in the lookup table data structure and in the communication protocols between the filter and the software that controls the rest of data acquisition.
- An alternative approach is to generate a second lookup table to provide a transmission correction factor for each bandpass center value and temperature.
- Software external to the filter controller software could independently read values from this file and apply corrections as needed to the raw data after it is collected from the camera. Both embodiments may implement parallel data recording of both the raw data and the corrected data.
- Another alternative embodiment may comprise developing a lookup table for instrument transmission characteristics for the whole system based at measurements on a NIST standard at each bandpass setting and operating temperature. This could be implemented as described in the alternative approach above. This may involve a measurement that carefully explored the operating space of the filter in terms of temperature and center bandpass. Two possible embodiments of such a method are provided for herein.
- the present disclosure provides for a method comprising: measuring or calculating the transmission over the operational wavelength range of each stage of the tunable filter at each environmental operating point (one or more of: temperature, humidity, atmospheric pressure), and at each set point for centerbandpass; determining parameters that report performance of the assembled filter in each operating state from the measured or calculated transmission data (state includes center bandpass, environmental conditions as listed above); performing the following: peak transmission, full width half maximum of transmission band, and area under transmission band, integrated out of band signal; creating a lookup table of one or more performance parameters (listed above) that is either: loaded into the filter control microprocessor memory or recorded in a data file stored in memory or media associated with the system in which the filter is integrated; and implementing a control software that sets the filter in response to some external electronic command and reports back to the software sending the external command the desired performance parameters through some communication mechanism and or protocol.
- the method may further comprise integrating out of band signal in spectral ranges limited to where detectors are sensitive can be performed.
- Another embodiment may comprise: measuring or calculating the transmission of the assembled filter stages at each environmental operating point and centerbandpass setpoint; determining parameters that report performance of the assembled filter in each operating state from the measured or calculated transmission data (state includes center bandpass, environmental conditions as listed above); performing the following: peak transmission, full width half maximum of transmission band, and area under transmission band, integrated out of band signal; creating a lookup table of one or more performance parameters (listed above) that is either: loaded into the filter control microprocessor memory or recorded in a data file stored in memory or media associated with the system in which the filter is integrated; and implementing a control software that sets the filter in response to some external electronic command and reports back to the software sending the external command the desired performance parameters through some communication mechanism and/or protocol.
- the method may further comprise integrating
- the present disclosure also provides for a method, illustrated by FIG. 5 , for filter modification based on transmission efficiency.
- the method 500 provides for acquiring test data at a first operating point in step 510 wherein said test data comprises an intensity response representative of a reference sample.
- the method 500 may further comprise acquiring said test data by illumination a reference sample to thereby generate a plurality of interacted photons, passing said plurality of interacted photons through a tunable filter, and detecting said plurality of interacted photons to thereby generate test data representative of said sample.
- the tunable filter may comprise a liquid crystal tunable filter, a multi-conjugate liquid-crystal tunable filter, and combinations thereof.
- Other embodiments of the present disclosure may utilize a device selected from the group consisting of: an acousto-optical tunable filter (“AOTF”), Evans Split-Element liquid crystal tunable filter, Solc liquid crystal tunable filter, Ferroelectric liquid crystal tunable filter, Fabry Perot liquid crystal tunable filter, a hybrid filter, and combinations thereof.
- AOTF acousto-optical tunable filter
- Evans Split-Element liquid crystal tunable filter Evans Split-Element liquid crystal tunable filter
- Solc liquid crystal tunable filter Solc liquid crystal tunable filter
- Ferroelectric liquid crystal tunable filter Ferroelectric liquid crystal tunable filter
- Fabry Perot liquid crystal tunable filter Fabry Perot liquid crystal tunable filter
- this test data may comprise at least one of Raman test data, infrared test data, and combinations thereof.
- Infrared test data may comprise at least one of: short wave infrared test data, near infrared test data, mid wave infrared test data, long wave infrared test data, and combinations thereof.
- Test data may comprise one or more hyperspectral images.
- the test data may comprise at least one of: a Raman hyperspectral image, an infrared hyperspectral image, and combinations thereof.
- An infrared hyperspectral image may comprise at least one of: a short wave infrared hyperspectral image, a near infrared hyperspectral image, a mid wave infrared hyperspectral image, a long wave infrared hyperspectral image, and combinations thereof.
- a look-up table may be searched based on an operating point to thereby determine an instrument response correction.
- the look-up table may comprise a plurality of instrument response corrections, wherein each instrument response correction corresponds to an intensity response representative of said reference sample at an operating point.
- This operating point may comprise an environmental operating point such as a temperature, a humidity, an atmospheric pressure, and combinations thereof.
- the method 500 may further comprise constructing one or more look-up tables by operating a system to thereby record an intensity response representative of a reference sample at each of a plurality of operating points.
- an instrument response correction may be applied to test data.
- the present disclosure also provides for a data storage medium containing program code, which when executed by a processor causes said processor to perform the following: acquire test data at a first operating point, wherein said test data comprises an intensity response representative of a reference sample; based on said first operating point, search a look-up table to thereby determine an instrument response correction, wherein said look-up table comprises a plurality of instrument response corrections, and wherein each instrument response correction corresponds to an intensity response representative of said reference sample at an operating point; and apply said instrument response correction to said test data.
- the data storage medium may further cause the processor to construct at least one look-up table. This may be achieved by operating a system to thereby record an intensity response representative of a reference sample at each of a plurality of operating points.
- This test data may be acquired by causing the processor to illuminate a reference sample to thereby generate a plurality of interacted photons, pass said interacted photons through a tunable filter, and detect said plurality of interacted photons to thereby generate test data representative of said reference sample.
- the present disclosure also provides for a system for filter modification based on transmission efficiency, one embodiment of which is illustrated in FIG. 6 .
- the system 600 may comprise an illumination source 610 configured to illuminate a sample 620 to thereby generate a first plurality of interacted photons.
- the illumination source 610 may comprise an active illumination source (e.g., a laser illumination source), a passive illumination source (e.g., a solar radiation source), and combinations thereof.
- Collection optics 630 may collect the plurality of interacted photons.
- the interacted photons may be passed through a tunable filter 640 .
- the tunable filter 640 may be configured so as to sequentially filter said plurality of interacted photons into a plurality of predetermined wavelength bands.
- the tunable filter 640 may comprise a liquid crystal tunable filter, a multi-conjugate liquid crystal tunable filter, and combinations thereof.
- the tunable filter 640 may also comprise an acousto-optical tunable filter (“AOTF”), Evans Split-Element liquid crystal tunable filter, Solc liquid crystal tunable filter, Ferroelectric liquid crystal tunable filter, Fabry Perot liquid crystal tunable filter, a hybrid filter, and combinations thereof.
- AOTF acousto-optical tunable filter
- Evans Split-Element liquid crystal tunable filter Solc liquid crystal tunable filter
- Ferroelectric liquid crystal tunable filter Ferroelectric liquid crystal tunable filter
- Fabry Perot liquid crystal tunable filter a hybrid filter, and combinations thereof.
- At least one detector 650 may be configured so as to detect said plurality of interacted photons and generate test data representative of said sample.
- the detector 650 may comprise a detector selected from the group consisting of: a CCD detector, an ICCD detector, an InGaAs detector, an extended range InGaAs detector, an InSb detector, a PtSi detector, a CMOS detector, a MCT detector, an intervac-intensified detector, a microbolometer, and combinations thereof.
- the detector 650 may be configured to generate test data which comprises at least one of: a test spectrum, a test image, and combinations thereof.
- This test image may comprise a hyperspectral test image.
- a sensor 660 may be configured so as to sense an operating point. This operating point may be received by a control unit 670 from a sensor 660 .
- the control unit 670 may be configured to search a look-up table based on an operating point (e.g., a temperature, a humidity, an atmospheric pressure) and determine an instrument response correction.
- the method 500 and the system 600 hold potential for actively providing an instrument response correction during data acquisition.
- This active feedback holds potential for enabling accurate and reliable determination of instrument response corrections. This may enable appropriate corrections for fluctuations in tunable filter performance due to environmental factors.
- FIGS. 7A , 7 B, 8 A, and 8 B are provided to illustrate transmission performance with respect to changes in temperature.
- FIG. 7A provides a data table representative of transmission efficiency for an exemplary SWIR multi-conjugate filter.
- FIG. 7B is a plot of this transmission v. temperature.
- FIG. 8A provides a data table representative of efficiency for an exemplary Raman multi-conjugate filter.
- FIG. 8B is a plot of this transmission v. temperature. It can be seen from the Figures how transmission efficiency is affected by the changes in temperature.
- the system and method of the present disclosure hold potential for overcoming the challenge of acquiring accurate and reliable transmission information with fluctuations in temperature.
Abstract
A system and method for providing an instrument response correction based on transmission efficiency. Test data may be acquired at a first operating point. A look-up table may be searched to determine an instrument response correction. This look-up table may comprise a plurality of instrument response corrections, each instrument response correction corresponding to an intensity response of the sample at an operating point. The instrument response correction may then be applied to correct for environmental factors that may affect transmission efficiency. A system may comprise an illumination source, a collection optics, a tunable filter, a detector, a sensor and a control unit. The detector may detect interacted photons generated by illuminating a sample and generate test data. The sensor may be configured to sense an operating condition and transmit this information to the control unit which is configured to search a look-up table to determine the appropriate instrument response correction.
Description
- This Application is a continuation-in-part of U.S. patent application Ser. No. 11/831,088, filed on Jul. 31, 2007, entitled “Optical Spectroscopy Instrument Response Correction,” and a continuation-in-part of U.S. patent application Ser. No. 11/900,169, filed on Sep. 10, 2007, entitled “Temperature Compensation in Liquid Crystal Tunable Filters.” This Application also claims priority under 35 U.S.C. 119(e) to the following U.S. Provisional Patent Applications: No. 61/303,814, filed on Feb. 12, 2010, entitled “System and Method for Calibration of Spectroscopic Systems Which Use Tunable Filters,” No. 61/324,963, filed on Apr. 16, 2010, entitled “Short-Wavelength Infrared (SWIR) Multi-Conjugate Liquid Crystal Tunable Filter,” No. 61/434,034, filed on Jan. 19, 2011, entitled “VIS-SNIR Multi-Conjugate Tunable Filter,” No. 61/460,816, filed on Jan. 7, 2011, entitled “Conformal Filter and Method for Use Thereof,” and No. 61/403,141, filed on Sep. 10, 2010, entitled “Systems and Methods for Improving Imaging Technology.” These applications are hereby incorporated by reference in their entireties.
- Spectroscopic imaging combines digital imaging and molecular spectroscopy techniques, which can include Raman scattering, fluorescence, photoluminescence, ultraviolet, visible and infrared absorption spectroscopies. When applied to the chemical analysis of materials, spectroscopic imaging is commonly referred to as chemical imaging. Instruments for performing spectroscopic (i.e. chemical) imaging typically comprise an illumination source, image gathering optics, focal plane array imaging detectors and imaging spectrometers.
- In general, the sample size determines the choice of image gathering optic. For example, a microscope is typically employed for the analysis of sub micron to millimeter spatial dimension samples. For larger objects, in the range of millimeter to meter dimensions, macro lens optics are appropriate. For samples located within relatively inaccessible environments, flexible fiberscope or rigid borescopes can be employed. For very large scale objects, such as planetary objects, telescopes are appropriate image gathering optics.
- For detection of images formed by the various optical systems, two-dimensional, imaging focal plane array (“FPA”) detectors are typically employed. The choice of FPA detector is governed by the spectroscopic technique employed to characterize the sample of interest. For example, silicon (“Si”) charge-coupled device (“CCD”) detectors or CMOS detectors are typically employed with visible wavelength fluorescence and Raman spectroscopic imaging systems, while indium gallium arsenide (“InGaAs”) FPA detectors are typically employed with near-infrared spectroscopic imaging systems.
- Wide-field spectroscopic imaging of a sample can be implemented by collecting spectra over the entire area encompassing the sample simultaneously using an electronically tunable optical imaging filter such as an acousto-optic tunable filter (“AOTF”) or a liquid crystal tunable filter (“LCTF”). Here, the organic material in such optical filters are actively aligned by applied voltages to produce the desired bandpass and transmission function. The spectra obtained for each pixel of such an image thereby forms a complex data set referred to as a hyperspectral image which contains the intensity values at numerous wavelengths or the wavelength dependence of each pixel element in this image.
- Spectroscopic devices operate over a range of wavelengths due to the operation ranges of the detectors or tunable filters possible. This enables analysis in the Ultraviolet (“UV”), visible (“VIS”), near infrared (“NIR”), short-wave infrared (“SWIR”), mid infrared (“MIR”) wavelengths, long wave infrared wavelengths (“LWIR”), and to some overlapping ranges. These correspond to wavelengths of approximately 180-380 nm (“UV”), 380-700 nm (“VIS”), 700-2500 nm (“NIR”), 850-1800 nm (“SWIR”), 650-1100 nm (“MWIR”), 400-1100 (“VIS-NIR”) and 1200-2450 (“LWIR”).
- In the case of Raman imaging data the real physical phenomenon being measured is the Raman scattered light emanating from a location in a field-of-view represented by a pixel in a data set. The Raman scattered light passes through a set of imaging optics to a detector. In general the optics are fixed components made of solid materials with stable optical characteristics. In full field-of-view Raman imaging of tissues, one of the optics is a liquid crystal tunable filter spectroscopic imaging element. This is a dynamically tunable narrow bandpass (−0.25 nm FWHM) filter that allows imaging of the same field-of-view at different wavelengths, without moving any optics. The specific advantages an approach based on this hardware are realized in the speed of acquisition and the alignment of images at different wavelengths. A disadvantage of this device is that there can be fluctuations in the transmission efficiency that depend on characteristics such as temperature, atmospheric pressure and humidity. These fluctuations are significantly larger than fluctuations of properties of standard physical optics in the same conditions and manifest themselves in the amount of light that is transmitted, and hence on the amount of Raman scattered light that is recorded at the detector. Because these fluctuations vary with environmental conditions, they manifest themselves differently at different operating conditions.
- Due to these fluctuations, an optical instrument operating in a real-life scenario does not have a perfect or ideal performance for all wavelengths of light. This is true at an optical component level, at an optical system level, or both. There exists a need for a system and method to overcome these limitations and provide an accurate and reliable means for determining transmission efficiency as it relates to temperature and other environmental conditions.
- The present disclosure relates to a system and method for correcting instrument response of an optical instrument. More specifically, the present disclosure relates to a system and method for correcting instrument response using an independent system with a known calibration.
- The accompanying drawings, which are included to provide further understanding of the disclosure and are incorporated in and constitute a part of this specification, illustrate embodiments of the disclosure and, together with the description, serve to explain the principles of the disclosure. The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.
- In the drawings:
-
FIG. 1A is illustrative of the wavelength to wavelength variation in transmission of a tunable filter. -
FIG. 1B is illustrative of the variance that occurs in filter transmission over time. -
FIG. 2 is representative of a method of the present disclosure. -
FIG. 3A illustrates an image and associated spectra for regions of a sample. -
FIG. 3B illustrates the same field of view asFIG. 3A after masking for pixels sampled by a dispersive spectrometer. -
FIG. 4 is illustrative of a system of the present disclosure. -
FIG. 5 is representative of a method of the present disclosure. -
FIG. 6 is illustrative of a system of the present disclosure. -
FIG. 7A is a data chart representative of an exemplary MCF SWIR filter's transmittance performance with respect to the temperature increment. -
FIG. 7B is a plot representative of an exemplary MCF SWIR filter's transmittance performance with respect to the temperature increment. -
FIG. 8A is a data chart representative of an exemplary MCF Raman filter's transmittance performance with respect to the temperature increment. -
FIG. 8B is a plot representative of an exemplary MCF Raman filter's transmittance performance with respect to the temperature increment. - Reference will now be made in detail to the preferred embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.
- The present disclosure provides for a system and method which hold potential for enabling the evaluation of an imperfect optical component or system in terms of its transmission or detection performance. In the case where the component or system is stable, the present disclosure contemplates that any deviations from the perfect or ideal performance may be measured and accounted for.
- If a spectrum of this source were taken with an ideal instrument, the spectrum would be a flat horizontal line as a function of wavelength. In one embodiment, an ideal light source that produces the same number of photons at each wavelength may be used. When this ideal source is used with an imperfect instrument, however, the measured spectrum is not a straight line. The real spectrum obtained from a perfect source with the same number of photons at each wavelength carries information about the instrument response of the real-world, imperfect optical instrument. The instrument response is the spectral response. In general, instrument response as a function of any number of parameters can be measured and corrected for.
- In working with optical systems, the presence of the instrument response—i.e., a manifestation of an instrument's imperfections or deviations from the ideal response—is evident in both dispersive and imaging spectroscopy experiments. For example, in case of a dispersive spectroscopy measurement (e.g., measurement of a Raman spectrum) on a sample with some background fluorescence, it is observed that the baseline on which the Raman spectrum sits is not a flat line. The features in the baseline (e.g., its lack of ideal flatness) have a characteristic that is due in part to the optical components and detectors that comprise the system used for the measurement.
- Direct measurement of molecules in intact biospecimens holds potential for enabling the evaluation of these samples without the use of antibody-, or gene-based complex biological reagents. Raman molecular imaging (“RMI”) may be one technology which holds potential for delivering this molecular information into the context of histopathological evaluation of tissue samples. RMI builds on the demonstrated success of Raman spectroscopy in the analysis of biological samples by integrating full field-of-view digital imaging with high precision spectrally sensitive optics. The system and method of the present disclosure hold potential for optimizing the instrumentation so that it can perform in a stable reproducible fashion to deliver this biological information to the clinicians on a routine basis. The present disclosure also contemplates that infrared imaging may hold similar potential for application in these scenarios.
- In particular the application of Raman imaging systems to tissue imaging applications requires a level of accuracy that is significantly higher than the requirement for standard use on relatively high concentration chemicals as in the pharmaceutical industry (where this technology finds its largest user base). The system and method of the present disclosure hold potential for enabling users to routinely apply this technology to tissue analysis, overcoming the limitations of the prior art. The system and method disclosed herein hold potential for delivering information directly from the molecules which comprise a tissue, without reagents, without destroying the sample so that subsequent evaluations can be performed.
- Variations in the transmission of a tunable filter can be demonstrated in a simple experiment by measuring the Raman scattering from a standard material through a liquid crystal tunable filter. The National Institute for Standards and Technology (“NIST”) provides a standard reference material (SRM 2242) that has a well characterized spectral response to laser excitation.
FIGS. 1A and 1B show a plot of this response with the mean intensity of an image of a piece of this material as a function of Raman shift acquired with a tunable filter-based system.FIG. 1A is illustrative of the wavelength to wavelength variation in the transmission of the tunable filter with the known spectrum of the material (red dashed line). A single frame of the image stack is shown to indicate the level of pixel to pixel to noise.FIG. 1B is illustrative of the detailed spectrum of the same measurement made on the same sample at a different time to indicate the variance that occurs in the filter transmission over time. - The Raman image is acquired over the full Raman scattering spectral range. The image is comprised of a series of 196 frames acquired at different center bandpass settings of the filter. The plot represented in red dashed line is the known spectrum of the material provided by NIST. The red solid line is the intensity of each frame versus center band setpoint. Along with the plot of mean intensity is shown the mean plus and minus the standard deviation of each frame (blue dotted lines). This is included to point out that the variance from frame to frame is not due to the pixel noise of the image (which is indicated by the standard deviations).
- The transmission spectrum is not smooth; it has sharp discontinuities and could not be well approximated by an analytic equation. The fundamental reason why these discontinuities exist is related to the operation of liquid crystal tunable filters as a collection of independently functioning liquid crystal elements stacked together.
- The tunable filter works by aligning the center bandpass of a series of liquid crystal elements which can each be independently adjusted in terms of a periodic (as a function of wavelength) transmission function. The overall bandpass of the filter is determined by the multiplication of the transmission of each of the elements. In order to select a specific center bandpass for the whole filter, an operating point is chosen for each element of the filter. During the manufacturing process the filter performance is optimized around high center bandpass throughput and high out-of-band light rejection. In order to perform this optimization, operating point choices are made that can lead to very different operating points for a given element at two adjacent wavelength setpoints. Because the choices of operating points are driven by out-of-band rejection, transmission smoothness is sacrificed. This is true about filters from multiple vendors with different designs.
- If the transmission function were constant, a simple ratiometric correction would be feasible. Data from a measurement identical to that shown in
FIGS. 1A and 1B on the same instrument and sample illustrates how this discontinuous transmission curve changes over time.FIG. 1B illustrates the mean and standard deviation spectra for a second measurement on the same instrument. The assumption here is that of all of the components in the system, the tunable filter is the least stable in terms of behavior over time. This assumption is supported by the clear presence of discontinuities consistent with filter reset points in the spectra shown and the fact that all of the other fixed optics in the system have smooth transmission functions over the relevant wavelength range. - An instrument response correction (“IRC”) relates a set of measurable physical properties (the truth) to the output of an instrument (the measurement). In the case of the measurement of Raman scattered light at any wavelength, λ, there is a simple relationship between the measured intensity and the actual number of photons that are emanating from a sample:
-
R(λ)Meas=α(λ)IRC ×R(λ)true - In this case αIRC is a unitless scalar that is essentially the transmission efficiency of the system at the wavelength being studied. Actual measurements are made in the units of output of the CCD camera. For the purposes of the relationship above, the unit conversions are ignored because they do not impact the instrument response correction and RMeas and Rtrue should be considered to include such unit conversions that are necessary to move them both into the unit of detector counts.
- In one embodiment, the present disclosure provides for a method incorporating the use of the SRM2242 from NIST. Based on the instructions for use the method involves: placing the standard sample in a Raman measurement system, measuring a spectrum of the material on the instrument, calculating an instrument response correction based on the known spectrum and the measured spectrum, using the instrument response correction spectrum to correct subsequent measurements on the system.
- This method may hold potential for systems which have a dispersing element and either a linear CCD detector, or some method of scanning the dispersing element as in a scanning monochromator. With measurements based on tunable filter technology the same basic approach may be taken where the measured spectrum is the spectrum at either a single pixel or the mean of spectra acquired at many pixels. Experimental measurements using this methodology may use the available NIST standard as a sample and existing equipment using Raman imaging systems integrating fixed optics and tunable filters from different manufacturers can be surveyed.
- In another embodiment, the present disclosure provides for a system and method for determining an instrument response correction by making a second measurement on the sample with an independent measurement system with established calibration.
- Dispersing spectrometers are built of fixed optical components with well understood drift and fluctuation due to environmental changes. Because of this established validation a dispersing spectrometer can be used as a plausible reference measurement used to correct measurements made with other devices.
- In one embodiment, the present disclosure contemplates the use of an independent measurement of the sample using a dispersing spectrometer as the true spectrum of the sample as the known reference value.
FIG. 2 illustrates one embodiment of the present disclosure. The method, 200, provides or illuminating a sample instep 210 to thereby generate a first plurality of interacted photons and a second plurality of interacted photons. This illumination may be achieved by utilizing at least one of active illumination and passive illumination. In an embodiment comprising active illumination, the illumination may be achieved using a laser light source. In an embodiment utilizing passive illumination, the illumination may be achieved using a solar radiation source. At least one of the first and second pluralities of interacted photons may comprise photons scattered by the sample, reflected by the sample, absorbed by the sample, emitted by the sample, and combinations thereof. - The system and method of the present disclosure hold potential for interrogating a wide variety of samples. In one embodiment, the sample may be a biological sample. In another embodiment, the sample may comprise a chemical sample, an explosive sample, a hazardous sample, a forensic sample, a pharmaceutical sample, and combinations thereof.
- A first plurality of interacted photons may be detected using a dispersive spectrometer in
step 220 to thereby generate at least one reference spectrum representative of said sample. In one embodiment, these photons may be transmitted to a dispersive spectrometer via a fiber optic. In one embodiment, this fiber optic may comprise a fiber array spectral translator device. This reference spectrum may comprise a Raman reference spectrum, an infrared reference spectrum, and combinations thereof. An infrared spectrum, as contemplated by the present disclosure, may comprise at least one of: a short-wave infrared reference spectrum, a near infrared reference spectrum, a mid-wave infrared spectrum, a long wave infrared spectrum, and combinations thereof. In one embodiment, multiple reference spectra representative of said sample may be obtained using a dispersive spectrometer. These reference spectra may then be assessed to determine a mean reference spectrum. - In step 230 a second plurality of interacted photons may be passed through a tunable filter. In one embodiment, this tunable filter may sequentially filter the second plurality of interacted photons into a plurality of predetermined wavelength bands. In one embodiment, the tunable filter may comprise technology available from ChemImage Corporation, Pittsburgh, Pa. This technology is more fully described in the following U.S. Patents and U.S. patent applications, which are hereby incorporated by reference in their entireties: U.S. Pat. No. 6,992,809, issued on Jan. 31, 2006, entitled “Multi-Conjugate Liquid Crystal Tunable Filter”; U.S. Pat. No. 7,362,489, issued on Apr. 22, 2008, also entitled “Multi-Conjugate Liquid Crystal Tunable Filter”; U.S. Provisional Patent Application No. 61/324,963, filed on Apr. 16, 2010, entitled “Short-Wavelength Infrared (SWIR) Multi-Conjugate Liquid Crystal Tunable Filter”; U.S. Provisional Patent Application No. 61/460,816, filed on Jan. 7, 2011, entitled “Conformal Filter and Method for Use Thereof”; and U.S. Provisional Patent Application No. 61/403,141, filed on Sep. 10, 2010, entitled “Systems and Methods for Improving Imaging Technology.”
- In one embodiment, the tunable filter may comprise a liquid crystal tunable filter, a multi-conjugate liquid-crystal tunable filter, and combinations thereof. Other embodiments of the present disclosure may utilize a device selected from the group consisting of: an acousto-optical tunable filter (“AOTF”), Evans Split-Element liquid crystal tunable filter, Solc liquid crystal tunable filter, Ferroelectric liquid crystal tunable filter, Fabry Perot liquid crystal tunable filter, a hybrid filter, and combinations thereof.
- Referring again to
FIG. 2 , themethod 200 provides for detecting a second plurality of interacted photons instep 240. Thisdetection 240 may be accomplished using an imaging detector and generate at least one hyperspectral test image representative of the sample. In one embodiment, this hyperspectral test image may comprise at least one of: a Raman hyperspectral image, an infrared hyperspectral image, and combinations thereof. This infrared hyperspectral image may be selected from the group consisting of: a short-wave infrared hyperspectral image, a near infrared hyperspectral image, a mid-wave infrared hyperspectral image, a long-wave infrared hyperspectral image, and combinations thereof. - In one embodiment, the
method 200 may detect said first and second plurality of photons substantially simultaneously. This embodiment holds potential for providing active feedback during operation. In another embodiment, themethod 200 may detect said first and second plurality of photons sequentially. - In
step 250, a hyperspectral test image may be assessed to thereby determine a mean test spectrum. This mean test spectrum may be representative of the mean intensity of a plurality of pixels in said hyperspectral test image. The mean test spectrum may be compared to a reference spectrum instep 260 to determine an instrument response correction. This comparison may be achieved by applying one or more chemometric techniques. Such techniques may include, but are not limited to, the following: principal component analysis (“PCA”), multivariate curve resolution (“MCR”), partial least squares discriminant analysis (“PLSDA”), k means clustering, band t. entropy method, adaptive subspace detector, cosine correlation analysis (“CCA”), Euclidian distance analysis (“EDA”), partial least squares regression (“PLSR”), spectral mixture resolution (“SMR”), a spectral angle mapper metric, a spectral information divergence metric, a Mahalanobis distance metric, a spectral unmixing algorithm, and combinations thereof. A spectral unmixing metric is disclosed in U.S. Pat. No. 7,072,770 entitled “Method for Identifying Components of a Mixture via Spectral Analysis,” which is hereby incorporated by reference in its entirety. Instep 270 an instrument response correction may be applied to said hyperspectral test image. - Application of an
instrument response correction 270 may result in an adjusted mean test spectrum associated with the test image. This adjusted mean test spectrum may be substantially equal to the reference spectrum obtained instep 220. - In one embodiment, the
method 200 may further comprise masking a hyperspectral test image. In such an embodiment, the mask may be such as to include those pixels sampled by said dispersive spectrometer and exclude those pixels not sampled by said dispersive spectrometer. - The base assumption is that the mean spectrum of the imaged area measured from a dispersive spectrometer should match the mean spectrum from the image acquired of the same area through the tunable filter. This type of measurement is feasible because the tunable filter only uses one polarization of the light emanating from the sample. Light with the unused polarization can be sent to a dispersing spectrometer and simultaneously measured to provide the reference spectrum. Key considerations relevant to this approach are: 1) to ensure that light collected with each polarization will have the same spectral distribution, 2) to ensure that spatial sampling and detection efficiency are matched for both arms of the measurement system, 3) to ensure that any sample changes during the course of the image based measurement are captured in the parallel dispersive spectrometer based measurement. This may be accomplished by masking the image of the sample to include only those pixels which are sampled by the dispersive spectrometer and acquiring multiple dispersive spectra which are combined to provide a synthesized reference spectrum which most accurately reflects what the image spectrum should be.
-
FIGS. 3A and 3B illustrate both a typical mask of where fibers sample a field of view of a microscope and the variation in spectral of some localized components of tissue which photobleach or photodegrade during the image acquisition.FIG. 3A illustrates an image and spectra from a Raman image of tissue. The spectra shown are from the two locations in the image indicating typical tissue signature 310 and localized fluorescent object 320.FIG. 3B illustrates the same field of view after masking for the pixels sampled by a dispersive spectrometer. The spectra shown are the mean spectrum of the image before 330 and after 340 the masking. - The present disclosure also provides for a system, illustrated by
FIG. 4 . Thesystem 400 may comprise anillumination source 410 configured to illuminate asample 420 to thereby generate a first plurality of interacted photons and a second plurality of interacted photons. In one embodiment, the system may comprise a platform for holding the sample. These interacted photons may be collected usingcollection optics 430. A first plurality of interacted photons may be transmitted to adispersive spectrometer 450 via afiber optic 440, which may comprise a fiber array spectral translator device (“FAST”). FAST technology may comprise technology available from ChemImage Corporation, Pittsburgh, Pa. A second plurality of interacted photons may be passed through atunable filter 460. Thistunable filter 460 may comprise a liquid crystal tunable filter, a multi-conjugate liquid crystal tunable filter, and combinations thereof. Thetunable filter 460 may also comprise an acousto-optical tunable filter (“AOTF”), Evans Split-Element liquid crystal tunable filter, Solc liquid crystal tunable filter, Ferroelectric liquid crystal tunable filter, Fabry Perot liquid crystal tunable filter, a hybrid filter, and combinations thereof. Thetunable filter 460 may be configured so as to sequentially filter interacted photons into a plurality of predetermined wavelength bands. - An
imaging detector 470 may be configured so as to detect a second plurality of interacted photons and generate at least one hyperspectral test image. Animaging detector 470 may comprise a Raman hyperspectral imaging detector, an infrared hyperspectral imaging detector, and combinations thereof. An infrared hyperspectral imaging detector may comprise at least one of: a short-wave infrared hyperspectral imaging detector, a near infrared hyperspectral imaging detector, a mid-wave infrared hyperspectral imaging detector, a long wave hyperspectral imaging detector, and combinations thereof. -
Imaging detector 470 may comprise a detector selected from the group consisting of: a CCD detector, an ICCD detector, an InGaAs detector, an extended range InGaAs detector, an InSb detector, a PtSi detector, a CMOS detector, a MCT detector, an intervac-intensified detector, a microbolometer, and combinations thereof. - The
system 400 may also be configured to operate in conjunction with one or more processors. In one embodiment, this processor may be configured so as to generate a mean spectrum representative of a hyperspectral test image, compare a mean spectrum to a reference spectrum, determine an instrument response correction, and apply an instrument response correction to a hyperspectral image. - The present disclosure also provides for a data storage medium containing program code, which when executed by a processor causes the processor to: illuminate a sample to generate a first plurality of interacted photons and a second plurality of interacted photons, detect a first plurality of interacted photons using a dispersive spectrometer to thereby generate a reference spectrum representative of a sample, pass a second plurality of interacted photons through a tunable filter, detect a second plurality of interacted photons using an imaging detector to thereby generate at least one hyperspectral test image, assess said hyperspectral test image to thereby determine a mean test spectrum wherein said mean test spectrum is representative of the mean intensity at each pixel in said hyperspectral test image, compare said mean test spectrum to a reference spectrum to thereby determine an instrument response correction, and apply said instrument response correction to said hyperspectral test image.
- The data storage medium, when executed by a processor may further cause the processor to obtain a plurality of reference spectra representative of a sample via said dispersive spectrometer and assess said plurality of reference spectra to thereby determine a mean reference spectrum representative of the sample. In another embodiment, the processor may further mask a hyperspectral test image so as to include a first plurality of pixels sampled by said dispersive spectrometer and exclude a second plurality of pixels not sampled by said dispersive spectrometer.
- The present discourse also provides for a method for correcting for instrument response by having the instrument actively report its current status and correct the data during acquisition. This is possible in the case where a user has access to fundamental data acquired during the manufacturing of the filter and the ability to use that information during operation of a filter. Such interaction holds potential for enabling modification to the communication to and from the filter in a way that holds potential for instrument response correction.
- In one embodiment, a filter control system may use a lookup table stored in memory to determine the proper set of control voltages for the stages that comprise the filter. This table may comprise a set of voltages for each possible bandpass center setpoint and operating temperature. When the filter is sent the command to tune to a specific bandpass center, the controller may query the temperature of the filter, refer to the lookup table to determine the appropriate control voltages for the temperature and center bandpass, then apply the appropriate voltage to each stage of the filter. To implement this method the controller may be modified to report the estimated transmission of the filter for the center bandpass and operating temperature.
- The present disclosure compensates a system and method to correct for variations in filter transmission. In one embodiment, this variation can be corrected at the filter controller level by changing the code in the filter controller software to read and report appropriate transmission values from an augmented data lookup table. This may also involve a change in the lookup table data structure and in the communication protocols between the filter and the software that controls the rest of data acquisition. An alternative approach is to generate a second lookup table to provide a transmission correction factor for each bandpass center value and temperature. Software external to the filter controller software could independently read values from this file and apply corrections as needed to the raw data after it is collected from the camera. Both embodiments may implement parallel data recording of both the raw data and the corrected data.
- Another alternative embodiment may comprise developing a lookup table for instrument transmission characteristics for the whole system based at measurements on a NIST standard at each bandpass setting and operating temperature. This could be implemented as described in the alternative approach above. This may involve a measurement that carefully explored the operating space of the filter in terms of temperature and center bandpass. Two possible embodiments of such a method are provided for herein. In one embodiment, the present disclosure provides for a method comprising: measuring or calculating the transmission over the operational wavelength range of each stage of the tunable filter at each environmental operating point (one or more of: temperature, humidity, atmospheric pressure), and at each set point for centerbandpass; determining parameters that report performance of the assembled filter in each operating state from the measured or calculated transmission data (state includes center bandpass, environmental conditions as listed above); performing the following: peak transmission, full width half maximum of transmission band, and area under transmission band, integrated out of band signal; creating a lookup table of one or more performance parameters (listed above) that is either: loaded into the filter control microprocessor memory or recorded in a data file stored in memory or media associated with the system in which the filter is integrated; and implementing a control software that sets the filter in response to some external electronic command and reports back to the software sending the external command the desired performance parameters through some communication mechanism and or protocol. In one embodiment, the method may further comprise integrating out of band signal in spectral ranges limited to where detectors are sensitive can be performed.
- Another embodiment may comprise: measuring or calculating the transmission of the assembled filter stages at each environmental operating point and centerbandpass setpoint; determining parameters that report performance of the assembled filter in each operating state from the measured or calculated transmission data (state includes center bandpass, environmental conditions as listed above); performing the following: peak transmission, full width half maximum of transmission band, and area under transmission band, integrated out of band signal; creating a lookup table of one or more performance parameters (listed above) that is either: loaded into the filter control microprocessor memory or recorded in a data file stored in memory or media associated with the system in which the filter is integrated; and implementing a control software that sets the filter in response to some external electronic command and reports back to the software sending the external command the desired performance parameters through some communication mechanism and/or protocol. In one embodiment, the method may further comprise integrating
- The present disclosure also provides for a method, illustrated by
FIG. 5 , for filter modification based on transmission efficiency. Themethod 500 provides for acquiring test data at a first operating point instep 510 wherein said test data comprises an intensity response representative of a reference sample. In one embodiment, themethod 500 may further comprise acquiring said test data by illumination a reference sample to thereby generate a plurality of interacted photons, passing said plurality of interacted photons through a tunable filter, and detecting said plurality of interacted photons to thereby generate test data representative of said sample. - In one embodiment, the tunable filter may comprise a liquid crystal tunable filter, a multi-conjugate liquid-crystal tunable filter, and combinations thereof. Other embodiments of the present disclosure may utilize a device selected from the group consisting of: an acousto-optical tunable filter (“AOTF”), Evans Split-Element liquid crystal tunable filter, Solc liquid crystal tunable filter, Ferroelectric liquid crystal tunable filter, Fabry Perot liquid crystal tunable filter, a hybrid filter, and combinations thereof.
- In one embodiment, this test data may comprise at least one of Raman test data, infrared test data, and combinations thereof. Infrared test data may comprise at least one of: short wave infrared test data, near infrared test data, mid wave infrared test data, long wave infrared test data, and combinations thereof. Test data may comprise one or more hyperspectral images. In one embodiment, the test data may comprise at least one of: a Raman hyperspectral image, an infrared hyperspectral image, and combinations thereof. An infrared hyperspectral image may comprise at least one of: a short wave infrared hyperspectral image, a near infrared hyperspectral image, a mid wave infrared hyperspectral image, a long wave infrared hyperspectral image, and combinations thereof.
- In step 520 a look-up table may be searched based on an operating point to thereby determine an instrument response correction. In one embodiment, the look-up table may comprise a plurality of instrument response corrections, wherein each instrument response correction corresponds to an intensity response representative of said reference sample at an operating point. This operating point may comprise an environmental operating point such as a temperature, a humidity, an atmospheric pressure, and combinations thereof. In one embodiment, the
method 500 may further comprise constructing one or more look-up tables by operating a system to thereby record an intensity response representative of a reference sample at each of a plurality of operating points. Instep 530 an instrument response correction may be applied to test data. - The present disclosure also provides for a data storage medium containing program code, which when executed by a processor causes said processor to perform the following: acquire test data at a first operating point, wherein said test data comprises an intensity response representative of a reference sample; based on said first operating point, search a look-up table to thereby determine an instrument response correction, wherein said look-up table comprises a plurality of instrument response corrections, and wherein each instrument response correction corresponds to an intensity response representative of said reference sample at an operating point; and apply said instrument response correction to said test data.
- In one embodiment, the data storage medium may further cause the processor to construct at least one look-up table. This may be achieved by operating a system to thereby record an intensity response representative of a reference sample at each of a plurality of operating points. This test data may be acquired by causing the processor to illuminate a reference sample to thereby generate a plurality of interacted photons, pass said interacted photons through a tunable filter, and detect said plurality of interacted photons to thereby generate test data representative of said reference sample.
- The present disclosure also provides for a system for filter modification based on transmission efficiency, one embodiment of which is illustrated in
FIG. 6 . Thesystem 600 may comprise anillumination source 610 configured to illuminate asample 620 to thereby generate a first plurality of interacted photons. Theillumination source 610 may comprise an active illumination source (e.g., a laser illumination source), a passive illumination source (e.g., a solar radiation source), and combinations thereof.Collection optics 630 may collect the plurality of interacted photons. The interacted photons may be passed through atunable filter 640. Thetunable filter 640 may be configured so as to sequentially filter said plurality of interacted photons into a plurality of predetermined wavelength bands. Thetunable filter 640 may comprise a liquid crystal tunable filter, a multi-conjugate liquid crystal tunable filter, and combinations thereof. Thetunable filter 640 may also comprise an acousto-optical tunable filter (“AOTF”), Evans Split-Element liquid crystal tunable filter, Solc liquid crystal tunable filter, Ferroelectric liquid crystal tunable filter, Fabry Perot liquid crystal tunable filter, a hybrid filter, and combinations thereof. - At least one
detector 650 may be configured so as to detect said plurality of interacted photons and generate test data representative of said sample. Thedetector 650 may comprise a detector selected from the group consisting of: a CCD detector, an ICCD detector, an InGaAs detector, an extended range InGaAs detector, an InSb detector, a PtSi detector, a CMOS detector, a MCT detector, an intervac-intensified detector, a microbolometer, and combinations thereof. - The
detector 650 may be configured to generate test data which comprises at least one of: a test spectrum, a test image, and combinations thereof. This test image may comprise a hyperspectral test image. Asensor 660 may be configured so as to sense an operating point. This operating point may be received by acontrol unit 670 from asensor 660. In one embodiment, thecontrol unit 670 may be configured to search a look-up table based on an operating point (e.g., a temperature, a humidity, an atmospheric pressure) and determine an instrument response correction. - The
method 500 and thesystem 600 hold potential for actively providing an instrument response correction during data acquisition. This active feedback holds potential for enabling accurate and reliable determination of instrument response corrections. This may enable appropriate corrections for fluctuations in tunable filter performance due to environmental factors. -
FIGS. 7A , 7B, 8A, and 8B are provided to illustrate transmission performance with respect to changes in temperature.FIG. 7A provides a data table representative of transmission efficiency for an exemplary SWIR multi-conjugate filter.FIG. 7B is a plot of this transmission v. temperature.FIG. 8A provides a data table representative of efficiency for an exemplary Raman multi-conjugate filter.FIG. 8B is a plot of this transmission v. temperature. It can be seen from the Figures how transmission efficiency is affected by the changes in temperature. The system and method of the present disclosure hold potential for overcoming the challenge of acquiring accurate and reliable transmission information with fluctuations in temperature. - The present disclosure may be embodied in other specific forms without departing from the spirit or essential attributes of the disclosure. Accordingly, reference should be made to the appended claims, rather than the foregoing specification, as indicating the scope of the disclosure. Although the foregoing description is directed to the embodiments of the disclosure, it is noted that other variations and modification will be apparent to those skilled in the art, and may be made without departing from the spirit or scope of the disclosure.
Claims (16)
1. A method comprising:
acquiring test data at a first operating point, wherein said test data comprises an intensity response representative of a reference sample;
based on said first operating point, searching a look-up table to thereby determine an instrument response correction, wherein said look-up table comprises:
a plurality of instrument response corrections, and
wherein each instrument response correction corresponds to an intensity response representative of said reference sample at an operating point; and
applying said instrument response correction to said test data.
2. The method of claim 1 further comprising constructing said look-up table by:
operating a system to thereby record an intensity response representative of a reference sample at each of a plurality of operating points.
3. The method of claim 1 wherein said test data comprises Raman test data.
4. The method of claim 3 wherein said Raman test data comprises a Raman hyperspectral image.
5. The method of claim 1 wherein said test data comprises test data selected from the group consisting of: short wave infrared test data, near infrared test data, mid wave infrared test data, long wave infrared test data, and combinations thereof.
6. The method of claim 5 wherein said short wave infrared test data comprises a short wave infrared hyperspectral image.
7. The method of claim 5 wherein said near infrared test data comprises a near infrared hyperspectral image.
8. The method of claim 5 wherein said mid wave infrared test data comprises a mid wave hyperspectral image.
9. The method of claim 5 wherein said long wave infrared test data comprises a long wave hyperspectral image.
10. The method of claim 1 further comprising, acquiring said test data by:
illuminating a reference sample to thereby generate a plurality of interacted photons;
passing said plurality of interacted photons through a tunable filter to thereby sequentially filter said plurality of interacted photons into a plurality of predetermined wavelength bands;
detecting said plurality of interacted photons to thereby generate test data representative of said reference sample.
11. The method of claim 1 wherein said operating point comprises an environmental operating point.
12. The method of claim 11 wherein said environmental operating point is selected from the group consisting of: a temperature, a humidity, an atmospheric pressure, and combinations thereof.
13. A data storage medium containing program code, which, when executed by a processor causes said processor to perform the following:
acquire test data at a first operating point, wherein said test data comprises an intensity response representative of a reference sample;
based on said first operating point, search a look-up table to thereby determine an instrument response correction, wherein said look-up table comprises
a plurality of instrument response corrections, and
wherein each instrument response correction corresponds to an intensity response representative of said reference sample at an operating point; and
apply said instrument response correction to said test data.
14. The data storage medium containing program code of claim 13 , which, when executed by a processor further causes said processor to construct said look-up table by:
operating a system to thereby record an intensity response representative of a reference sample at each of a plurality of operating points.
15. The data storage medium containing program code of claim 13 , which, when executed by a processor further causes said processor to acquire said test data by:
illuminating a reference sample to thereby generate a plurality of interacted photons;
passing said plurality of interacted photons through a tunable filter to thereby sequentially filter said plurality of interacted photons into a plurality of predetermined wavelength bands;
detecting said plurality of interacted photons to thereby generate test data representative of said reference sample.
16. A system comprising:
an illumination source to illuminate a sample to thereby generate a first plurality of interacted photons;
a collection optics configured to collect said first plurality of interacted photons;
a liquid crystal-based tunable optical filter configured to sequentially filter said first plurality of interacted photons into a plurality of predetermined wavelength bands;
at least one detector configured to detect said first plurality of interacted photons and thereby generate test data representative of said sample;
at least one sensor configured so as to sense at least one operating point;
a control unit configured to:
receive said operating point from said sensor, and
based on said operating point, searching a look-up table to thereby determine an instrument response correction.
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US12/931,836 US20110208462A1 (en) | 2007-07-31 | 2011-02-11 | System and method for instrument correction using transmission efficiency |
US13/347,788 US9464934B2 (en) | 2011-01-11 | 2012-01-11 | System and method for correcting spectral response using a radiometric correction filter |
Applications Claiming Priority (8)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US11/831,088 US20080034833A1 (en) | 2006-07-31 | 2007-07-31 | Optical Spectroscopy Instrument Response Correction |
US11/900,169 US20080062353A1 (en) | 2006-09-08 | 2007-09-10 | Temperature compensation in liquid crystal tunable filters |
US30381410P | 2010-02-12 | 2010-02-12 | |
US32496310P | 2010-04-16 | 2010-04-16 | |
US40314110P | 2010-09-10 | 2010-09-10 | |
US201161460816P | 2011-01-07 | 2011-01-07 | |
US201161434034P | 2011-01-19 | 2011-01-19 | |
US12/931,836 US20110208462A1 (en) | 2007-07-31 | 2011-02-11 | System and method for instrument correction using transmission efficiency |
Related Parent Applications (2)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US11/831,088 Continuation-In-Part US20080034833A1 (en) | 2006-07-31 | 2007-07-31 | Optical Spectroscopy Instrument Response Correction |
US12/931,868 Continuation-In-Part US8537354B2 (en) | 2007-07-31 | 2011-02-11 | System and method for instrument response correction based on independent measurement of the sample |
Related Child Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US13/347,788 Continuation-In-Part US9464934B2 (en) | 2011-01-11 | 2012-01-11 | System and method for correcting spectral response using a radiometric correction filter |
Publications (1)
Publication Number | Publication Date |
---|---|
US20110208462A1 true US20110208462A1 (en) | 2011-08-25 |
Family
ID=44477222
Family Applications (2)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US12/931,868 Active 2028-04-26 US8537354B2 (en) | 2007-07-31 | 2011-02-11 | System and method for instrument response correction based on independent measurement of the sample |
US12/931,836 Abandoned US20110208462A1 (en) | 2007-07-31 | 2011-02-11 | System and method for instrument correction using transmission efficiency |
Family Applications Before (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US12/931,868 Active 2028-04-26 US8537354B2 (en) | 2007-07-31 | 2011-02-11 | System and method for instrument response correction based on independent measurement of the sample |
Country Status (1)
Country | Link |
---|---|
US (2) | US8537354B2 (en) |
Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20140354996A1 (en) * | 2010-03-10 | 2014-12-04 | Drexell University | Tunable electro-optic filter stack |
US20160091704A1 (en) * | 2014-09-29 | 2016-03-31 | Agilent Technologies, Inc. | Mid-Infrared Scanning System |
WO2017017684A1 (en) * | 2015-07-30 | 2017-02-02 | Technology Innovation Momentum Fund (Israel) Limited Partnership | Spectral imaging method and system |
US9625878B2 (en) | 2009-03-10 | 2017-04-18 | Drexel University | Dynamic time multiplexing fabrication of holographic polymer dispersed liquid crystals for increased wavelength sensitivity |
WO2019025564A1 (en) * | 2017-08-04 | 2019-02-07 | Carl Zeiss Jena Gmbh | Sample-based gas quality control by means of raman spectroscopy |
US10229476B2 (en) | 2013-06-24 | 2019-03-12 | Technology Innovation Momentum Fund (Israel) Limited Partnership | System and method for color image acquisition |
US10827152B2 (en) | 2015-07-15 | 2020-11-03 | Technology Innovation Momentum Fund (Israel) Limited Partnership | Tunable MEMS etalon |
Families Citing this family (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US8629411B2 (en) * | 2010-07-13 | 2014-01-14 | First Solar, Inc. | Photoluminescence spectroscopy |
JP2013181912A (en) * | 2012-03-02 | 2013-09-12 | Seiko Epson Corp | Component analyzer |
US20140267684A1 (en) * | 2013-03-15 | 2014-09-18 | Chemlmage Corporation | System and method for detecting contamination in food using hyperspectral imaging |
US11287384B2 (en) * | 2020-07-17 | 2022-03-29 | Endress+Hauser Optical Analysis, Inc. | System and method for improving calibration transfer between multiple raman analyzer installations |
Citations (12)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5113275A (en) * | 1991-07-03 | 1992-05-12 | Bell Communications Research, Inc. | Temperature compensation of liquid-crystal etalon filters |
US5247378A (en) * | 1991-06-07 | 1993-09-21 | Peter Miller | Optical retarder having means for determining the retardance of the cell corresponding to the sensed capacitance thereof |
US5568286A (en) * | 1993-10-04 | 1996-10-22 | General Electric Company | Fast liquid crystal switching unit |
US5850623A (en) * | 1997-03-14 | 1998-12-15 | Eastman Chemical Company | Method for standardizing raman spectrometers to obtain stable and transferable calibrations |
US6353656B1 (en) * | 1998-07-24 | 2002-03-05 | Technology For Energy Corporation | Radioisotope based x-ray residual stress analysis apparatus |
US6403947B1 (en) * | 1999-03-18 | 2002-06-11 | Cambridge Research & Instrumentation Inc. | High-efficiency multiple probe imaging system |
US6775688B1 (en) * | 1999-04-09 | 2004-08-10 | Canon Kabushiki Kaisha | Data processing apparatus and data processing method |
US6801310B2 (en) * | 2001-11-07 | 2004-10-05 | Arroyo Optics, Inc. | Liquid crystal modulator and polarization diversity optics for optical communications |
US20070216898A1 (en) * | 2003-07-18 | 2007-09-20 | Gardner Charles W Jr | Sample container and system for a handheld spectrometer and method for using therefor |
US20080034833A1 (en) * | 2006-07-31 | 2008-02-14 | John Maier | Optical Spectroscopy Instrument Response Correction |
US20080062353A1 (en) * | 2006-09-08 | 2008-03-13 | Chemlmage Corporation | Temperature compensation in liquid crystal tunable filters |
US7595873B1 (en) * | 2008-02-11 | 2009-09-29 | Thermo Electron Scientific Instruments Llc | Rapid spatial averaging over an extended sample in a Raman spectrometer |
Family Cites Families (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20030135122A1 (en) * | 1997-12-12 | 2003-07-17 | Spectrx, Inc. | Multi-modal optical tissue diagnostic system |
US6717668B2 (en) * | 2000-03-07 | 2004-04-06 | Chemimage Corporation | Simultaneous imaging and spectroscopy apparatus |
EP1463926A4 (en) | 2002-01-10 | 2010-09-08 | Chemimage Corp | Method for detection of pathogenic microorganisms |
-
2011
- 2011-02-11 US US12/931,868 patent/US8537354B2/en active Active
- 2011-02-11 US US12/931,836 patent/US20110208462A1/en not_active Abandoned
Patent Citations (12)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5247378A (en) * | 1991-06-07 | 1993-09-21 | Peter Miller | Optical retarder having means for determining the retardance of the cell corresponding to the sensed capacitance thereof |
US5113275A (en) * | 1991-07-03 | 1992-05-12 | Bell Communications Research, Inc. | Temperature compensation of liquid-crystal etalon filters |
US5568286A (en) * | 1993-10-04 | 1996-10-22 | General Electric Company | Fast liquid crystal switching unit |
US5850623A (en) * | 1997-03-14 | 1998-12-15 | Eastman Chemical Company | Method for standardizing raman spectrometers to obtain stable and transferable calibrations |
US6353656B1 (en) * | 1998-07-24 | 2002-03-05 | Technology For Energy Corporation | Radioisotope based x-ray residual stress analysis apparatus |
US6403947B1 (en) * | 1999-03-18 | 2002-06-11 | Cambridge Research & Instrumentation Inc. | High-efficiency multiple probe imaging system |
US6775688B1 (en) * | 1999-04-09 | 2004-08-10 | Canon Kabushiki Kaisha | Data processing apparatus and data processing method |
US6801310B2 (en) * | 2001-11-07 | 2004-10-05 | Arroyo Optics, Inc. | Liquid crystal modulator and polarization diversity optics for optical communications |
US20070216898A1 (en) * | 2003-07-18 | 2007-09-20 | Gardner Charles W Jr | Sample container and system for a handheld spectrometer and method for using therefor |
US20080034833A1 (en) * | 2006-07-31 | 2008-02-14 | John Maier | Optical Spectroscopy Instrument Response Correction |
US20080062353A1 (en) * | 2006-09-08 | 2008-03-13 | Chemlmage Corporation | Temperature compensation in liquid crystal tunable filters |
US7595873B1 (en) * | 2008-02-11 | 2009-09-29 | Thermo Electron Scientific Instruments Llc | Rapid spatial averaging over an extended sample in a Raman spectrometer |
Cited By (20)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US9625878B2 (en) | 2009-03-10 | 2017-04-18 | Drexel University | Dynamic time multiplexing fabrication of holographic polymer dispersed liquid crystals for increased wavelength sensitivity |
US20140354996A1 (en) * | 2010-03-10 | 2014-12-04 | Drexell University | Tunable electro-optic filter stack |
US9752932B2 (en) * | 2010-03-10 | 2017-09-05 | Drexel University | Tunable electro-optic filter stack |
US10175106B2 (en) | 2010-10-29 | 2019-01-08 | Drexel University | Tunable electro-optic filter stack |
US10229476B2 (en) | 2013-06-24 | 2019-03-12 | Technology Innovation Momentum Fund (Israel) Limited Partnership | System and method for color image acquisition |
US20160091704A1 (en) * | 2014-09-29 | 2016-03-31 | Agilent Technologies, Inc. | Mid-Infrared Scanning System |
CN105466886A (en) * | 2014-09-29 | 2016-04-06 | 安捷伦科技有限公司 | Mid-infrared scanning system |
US11300773B2 (en) * | 2014-09-29 | 2022-04-12 | Agilent Technologies, Inc. | Mid-infrared scanning system |
US10827152B2 (en) | 2015-07-15 | 2020-11-03 | Technology Innovation Momentum Fund (Israel) Limited Partnership | Tunable MEMS etalon |
US20180209850A1 (en) * | 2015-07-30 | 2018-07-26 | Technology Innovation Momentum Fund (Israel) Limited Partnership | Spectral imaging method and system |
CN108291800A (en) * | 2015-07-30 | 2018-07-17 | 科技创新动量基金(以色列)有限责任合伙公司 | Spectrum imaging method and system |
IL256975A (en) * | 2015-07-30 | 2018-03-29 | Tech Innovation Momentum Fund Israel Limited Partnership | Spectral imaging method and system |
KR102049373B1 (en) | 2015-07-30 | 2019-11-27 | 테크놀로지 이노베이션 모멘텀 펀드 (이스라엘) 리미티드 파트너쉽 | Spectrum Image Processing Method, Spectrum Image Processing System and Control Unit |
US10605660B2 (en) * | 2015-07-30 | 2020-03-31 | Technology Innovation Momentum Fund (Israel) Limited Partnership | Spectral imaging method and system |
WO2017017684A1 (en) * | 2015-07-30 | 2017-02-02 | Technology Innovation Momentum Fund (Israel) Limited Partnership | Spectral imaging method and system |
CN108291800B (en) * | 2015-07-30 | 2021-07-13 | 科技创新动量基金(以色列)有限责任合伙公司 | Spectral imaging method and system |
KR20180030995A (en) * | 2015-07-30 | 2018-03-27 | 테크놀로지 이노베이션 모멘텀 펀드 (이스라엘) 리미티드 파트너쉽 | Spectrum image processing method and system |
WO2019025564A1 (en) * | 2017-08-04 | 2019-02-07 | Carl Zeiss Jena Gmbh | Sample-based gas quality control by means of raman spectroscopy |
CN110998289A (en) * | 2017-08-04 | 2020-04-10 | 卡尔蔡司耶拿有限责任公司 | Sample-based gas quality control by raman spectroscopy |
US11460407B2 (en) | 2017-08-04 | 2022-10-04 | Carl Zeiss Jena Gmbh | Sample-based gas quality control by means of raman spectroscopy |
Also Published As
Publication number | Publication date |
---|---|
US20110211763A1 (en) | 2011-09-01 |
US8537354B2 (en) | 2013-09-17 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US8537354B2 (en) | System and method for instrument response correction based on independent measurement of the sample | |
US9464934B2 (en) | System and method for correcting spectral response using a radiometric correction filter | |
US9041932B2 (en) | Conformal filter and method for use thereof | |
US7486395B2 (en) | System and method for a chemical imaging threat assessor with a probe | |
US9581499B2 (en) | System and method for optical measurement of a target | |
US9157800B2 (en) | System and method for assessing analytes using conformal filters and dual polarization | |
US7738095B2 (en) | Method and apparatus for compact spectrometer for detecting hazardous agents | |
US9052290B2 (en) | SWIR targeted agile raman system for detection of unknown materials using dual polarization | |
US8547540B2 (en) | System and method for combined raman and LIBS detection with targeting | |
US7440096B2 (en) | Method and apparatus for compact spectrometer for fiber array spectral translator | |
US9869585B2 (en) | Dual spectrometer | |
US7548310B2 (en) | Method and apparatus for compact spectrometer for multipoint sampling of an object | |
US8994938B2 (en) | Raman spectroscopy using diffractive MEMS | |
US20140267684A1 (en) | System and method for detecting contamination in food using hyperspectral imaging | |
US20120134582A1 (en) | System and Method for Multimodal Detection of Unknown Substances Including Explosives | |
US20100309464A1 (en) | Raman Chemical Imaging of Threat Agents Using Pulsed Laser Excitation and Time-Gated Detection | |
WO2006007063A2 (en) | Method and apparatus for peak compensation in an optical filter | |
US20170146403A1 (en) | System and method for detecting target materials using a vis-nir detector | |
Lerner et al. | Approaches to spectral imaging hardware | |
US8525987B2 (en) | Method for operating an optical filter in multiple modes | |
Saari et al. | Handheld hyperspectral imager | |
US20140042322A1 (en) | Portable System and Method for Detecting Drug Materials | |
US20170160189A1 (en) | Optical analysis system and process | |
US11879777B2 (en) | Cellphone-based raman spectrometer system for the detection and identification of chemical and biological molecules | |
Thigpen et al. | Photometric calibration for quantitative spectral microscopy under transmitted illumination |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
AS | Assignment |
Owner name: CHEMIMAGE CORPORATION, PENNSYLVANIA Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:MAIER, JOHN;FUHRMAN, MICHAEL;SIGNING DATES FROM 20110428 TO 20110503;REEL/FRAME:026212/0933 |
|
AS | Assignment |
Owner name: CHEMIMAGE TECHNOLOGIES LLC, PENNSYLVANIA Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:CHEMIMAGE CORPORATION;REEL/FRAME:030573/0454 Effective date: 20130530 |
|
STCB | Information on status: application discontinuation |
Free format text: ABANDONED -- FAILURE TO RESPOND TO AN OFFICE ACTION |