Method and apparatus for automated spectral calibration

Abstract

The disclosure generally relates to a method and apparatus for automated spectral calibration of a spectroscopy device. In one embodiment, the disclosure relates to a method for simultaneous calibration and spectral imaging of a sample by: simultaneously illuminating the sample and a calibrant with a plurality of illuminating photons; receiving, at the spectrometer, a first plurality of photons collected from the sample and a second plurality of photons collected from the calibrant; forming a calibrant spectrum from the first plurality of collected photons and a sample spectrum from the second plurality of collected photons; comparing the calibrant spectrum with a reference spectrum of the calibrant to determine a wavelength-shift in the calibrant spectrum; applying the wavelength-shift to the sample spectrum to obtain a calibrated sample spectrum.

1 . A method for simultaneous calibration and spectral imaging of a sample comprising: 
 simultaneously illuminating the sample and a calibrant with a plurality of illuminating photons;    receiving, at the spectrometer, a first plurality of photons collected from the sample and a second plurality of photons collected from the calibrant;    forming a calibrant spectrum from the first plurality of collected photons and a sample spectrum from the second plurality of collected photons;    comparing the calibrant spectrum with a reference spectrum of the calibrant to determine a wavelength-shift in the calibrant spectrum;    applying the wavelength-shift to the sample spectrum to obtain a calibrated sample spectrum.    
     
     
         2 . The method of  claim 1 , wherein the photons collected from the sample are selected from the group consisting of photons reflected, refracted, emitted, scattered, transmitted and absorbed, and by the sample.  
     
     
         3 . The method of  claim 1 , wherein the sample spectrum is one of a Raman spectrum, visible absorption spectrum, near infrared absorption spectrum, infrared absorption spectrum or fluorescence spectrum.  
     
     
         4 . The method of  claim 1 , wherein the calibrant is selected from the group consisting of acetaminophen, polymethyl methacrylate, oxygen and nitrogen, neon, krypton, xenon, BK-7 glass, quartz, fused silica, naphthalene, 1,4 bis(2-methylstyryl)benzene, sulfur, toluene, acetonitrile, benzonitrile, cyclohexane, polystyrene, dysprosium oxide, and holmium oxide.  
     
     
         5 . The method of  claim 1 , wherein the spectrometer is a dispersive spectrometer.  
     
     
         6 . The method of  claim 1 , wherein the spectrometer is an imaging spectrometer.  
     
     
         7 . The method of  claim 6 , wherein the imaging spectrometer is a liquid crystal tunable filter.  
     
     
         8 . The method of  claim 1 , wherein the plurality of illuminating photons have a first wavelength.  
     
     
         9 . The method of  claim 1 , wherein the step of receiving the plurality of photons collected from the sample and the plurality of photons collected from the calibrant further comprises separating the photons collected from the sample from the photons collected from the calibrant.  
     
     
         10 . The method of  claim 1 , wherein the step of receiving the plurality of photons collected from the sample and the plurality of photons collected from the calibrant further comprises filtering the received photons to remove photons of an undesired wavelength.  
     
     
         11 . A system for simultaneous calibration and dispersive and/or spectral imaging of a sample comprising: 
 an input for simultaneously receiving a first plurality of photons collected from the sample and a second plurality of photons collected from a calibrant;    a spectrograph for forming a sample spectrum from the first plurality of photons and a calibrant spectrum from the second plurality of photons;    a first processor for comparing the calibrant spectrum with a reference spectrum of the calibrant to determine a wavelength-shift in the calibrant spectrum; and    a second processor for applying the wavelength-shift to the sample spectrum to obtain a calibrated sample spectrum.    
     
     
         12 . The system of  claim 11 , wherein the photons collected from the sample are selected from the group consisting of photons reflected, refracted, luminescence, fluorescence, Raman scattered, transmitted, absorbed, and emitted by the sample.  
     
     
         13 . The system of  claim 11 , further comprising an illumination source for simultaneously illuminating the sample and a calibrant with a plurality of illuminating photons.  
     
     
         14 . The system of  claim 11 , wherein the first processor and the second processor define one processor.  
     
     
         15 . The system of  claim 11 , further comprising a memory for storing and communicating the reference spectrum of the calibrant to the first processor.  
     
     
         16 . The system of  claim 11 , wherein the first processor is programmed with instructions to: 
 a) determine a plurality of peak locations in the calibrant spectrum;    b) determine a plurality of peak locations in the reference spectrum of the calibrant;    c) compare the plurality of peak locations in the calibrant spectrum with a plurality of corresponding peak locations in the reference spectrum of the calibrant; and    d) determine the wavelength-shift as a function of the comparison between at least one peak location in the calibrant spectrum and a corresponding peak location in the reference spectrum.    
     
     
         17 . The system of claim  1 l, wherein the second processor is programmed with instructions to: 
 a) receive the sample spectrum from the spectrograph;    b) receive the wavelength-shift from the first processor; and    b) calibrate the sample spectrum as a function of the wavelength-shift.    
     
     
         18 . The system of  claim 11 , wherein the sample spectrum is one of a Raman spectrum, visible absorption spectrum, near infrared absorption spectrum, infrared absorption spectrum or fluorescence spectrum.  
     
     
         19 . The system of  claim 11 , wherein the calibrant is selected from the group consisting of acetaminophen, polymethyl methacrylate, oxygen and nitrogen, neon, krypton, xenon, BK-7 glass, quartz, fused silica, naphthalene, 1,4 bis(2-methylstyryl)benzene, sulfur, toluene, acetonitrile, benzonitrile, cyclohexane, polystyrene, dysprosium oxide, and holmium oxide.  
     
     
         20 . The system of  claim 11 , wherein the spectrometer is a dispersive spectrometer.  
     
     
         21 . The system of  claim 11 , wherein the spectrometer is an imaging spectrometer.  
     
     
         22 . The system of  claim 21 , wherein the imaging spectrometer is a liquid crystal tunable filter.  
     
     
         23 . The system of  claim 11 , wherein the illuminating photons have a first wavelength.  
     
     
         24 . The system of  claim 11 , further comprising a medium for communicating the first plurality of photons collected from by the sample and the second plurality of photons collected from the calibrant.  
     
     
         25 . The system of  claim 24 , wherein the medium is an optical fiber.  
     
     
         26 . The system of  claim 11 , further comprising a first medium for communicating the first plurality of photons collected from the sample and a second medium for communicating the second plurality of photons collected from the calibrant.  
     
     
         27 . The system of  claim 11 , further comprising an optical splitter for directing a first plurality of illuminating photons to the sample and a second plurality of illuminating photons to the calibrant.  
     
     
         28 . An apparatus for simultaneous calibration and dispersive and/or spectral image acquisition of a sample, comprising: 
 a processing circuit for simultaneously receiving a calibrant spectrum and a sample spectrum, and    a memory in communication with the processing circuit, the memory storing instructions for the processing circuit to: 
 process the calibrant spectrum to locate and identify a plurality of peaks,  
 compare the plurality of peak locations in the calibrant spectrum with a plurality of corresponding peak locations in a reference spectrum of the calibrant, and  
 determine a wavelength-shift as a function of a comparison between at least one peak location in the calibrant spectrum and a corresponding peak location in the reference spectrum;  
 calibrate the sample spectrum by applying the wavelength-shift to the sample spectrum.  
   
     
     
         29 . The apparatus of  claim 28 , wherein applying the wavelength-shift further comprises: 
 (a) identifying a plurality of peak locations in the sample spectrum; and    (b) applying the wavelength-shift to at least one of the plurality of peak locations in the sample spectrum.    
     
     
         30 . The apparatus of  claim 28 , further comprising a database for storing a reference spectrum of the calibrant.  
     
     
         31 . The apparatus of  claim 28 , wherein the processing circuit comprises at least one microprocessor.  
     
     
         32 . The apparatus of  claim 28 , wherein the apparatus is a spectrometer.  
     
     
         33 . The apparatus of  claim 28 , wherein the sample spectrum is one of a Raman spectrum, visible absorption spectrum, near infrared absorption spectrum, infrared absorption spectrum or fluorescence spectrum.  
     
     
         34 . The apparatus of  claim 28 , wherein the calibrant is selected from the group consisting of acetaminophen, polymethyl methacrylate, oxygen and nitrogen, neon, krypton, xenon, BK-7 glass, quartz, fused silica, naphthalene, 1,4 bis(2-methylstyryl)benzene, sulfur, toluene, acetonitrile, benzonitrile, cyclohexane, polystyrene, dysprosium oxide, and holmium oxide.  
     
     
         35 . The apparatus of  claim 28 , wherein the spectrometer is a dispersive spectrometer.  
     
     
         36 . The apparatus of  claim 28 , wherein the spectrometer is an imaging spectrometer.  
     
     
         37 . The apparatus of  claim 28 , wherein the imaging spectrometer is a liquid crystal tunable filter.  
     
     
         38 . A method for simultaneous calibration and imaging of a sample in a spectrometer, the method comprising: 
 simultaneously illuminating the sample and an intrinsic calibrant with a plurality of illuminating photons;    receiving, at the spectrometer, a first plurality of photons collected from the sample and a second plurality of photons collected from the intrinsic calibrant;    forming a sample spectrum from the first plurality of photons and an intrinsic calibrant spectrum from the second plurality of photons;    comparing the intrinsic calibrant spectrum with a reference spectrum for said intrinsic calibrant to determine a wavelength-shift in the calibrant spectrum;    applying the wavelength-shift to the sample spectrum to obtain a calibrated sample spectrum.    
     
     
         39 . The method of  claim 38 , wherein imaging defines at least one of obtaining dispersive spectral data or spectral imaging data from the sample.  
     
     
         40 . The method of  claim 38 , wherein the first plurality of photons collected from the sample are selected from the group consisting of photons reflected, refracted, luminescence, fluorescence, Raman scattered, transmitted, absorbed, and emitted by the sample.  
     
     
         41 . The method of  claim 38 , wherein the intrinsic calibrant is selected from the group consisting of acetaminophen, polymethyl methacrylate, oxygen and nitrogen, neon, krypton, xenon, BK-7 glass, quartz, fused silica, naphthalene, 1,4 bis(2-methylstyryl)benzene, sulfur, toluene, acetonitrile, benzonitrile, cyclohexane, polystyrene, dysprosium oxide, and holmium oxide.  
     
     
         42 . The method of  claim 38 , wherein the sample spectrum is one of a Raman spectrum, near infrared spectrum absorption/reflectance, infrared spectrum absorption/reflectance, visible absorption/reflectance or fluorescent spectrum.  
     
     
         43 . The method of  claim 38 , wherein the spectrometer is a dispersive spectrometer.  
     
     
         44 . The method of  claim 38 , wherein the spectrometer is an imaging spectrometer.  
     
     
         45 . The method of  claim 38 , wherein the imaging spectrometer is a liquid crystal tunable filter.  
     
     
         46 . The method of  claim 38 , wherein the plurality of illuminating photons have a first wavelength.  
     
     
         47 . The method of  claim 38 , wherein the step of receiving the first plurality of photons from the sample and the second plurality of photons from the calibrant further comprises separating the first plurality of photons from the second plurality of photons.  
     
     
         48 . The method of  claim 38 , wherein the step of receiving the first plurality of photons from the sample and the second plurality of photons from the calibrant further comprises filtering the received photons to remove photons of an undesired wavelength.  
     
     
         49 . A system for simultaneous calibration and spectral imaging of a sample, the system comprising: 
 an optical train containing an intrinsic calibrant and having a first optical path and a second optical path, the first optical path simultaneously illuminating the sample and the intrinsic calibrant with a plurality of illuminating photons and a second optical path collecting a first plurality of photons from the sample and a second plurality of photons from the intrinsic calibrant;    a spectrograph for forming a sample spectrum from the first plurality of photons and an intrinsic calibrant spectrum from the second plurality of photons;    a first processing circuitry for comparing the intrinsic calibrant spectrum with a reference spectrum for the intrinsic calibrant to determine a wavelength-shift; and    a second processing circuitry for obtaining a calibrated sample spectrum by applying the wavelength-shift to the sample spectrum.    
     
     
         50 . The system of  claim 49 , wherein the first plurality of photons are selected from the group consisting of photons reflected, refracted, luminescence, fluorescence, Raman scattered, transmitted, absorbed, and emitted by the sample.  
     
     
         51 . The system of  claim 49 , further comprising an illumination source.  
     
     
         52 . The system of  claim 49 , wherein the optical train further comprises an objective lens.  
     
     
         53 . The system of  claim 49 , wherein the intrinsic calibrant is coated on a portion of the objective lens.  
     
     
         54 . The system of  claim 49 , wherein the first optical path is a fiber optic medium.  
     
     
         55 . The system of  claim 49 , wherein the second optical path defines a bifurcated optical fiber.  
     
     
         56 . The system of  claim 49 , wherein the first processing circuitry further comprises at least one microprocessor in communication with a memory.  
     
     
         57 . The system of  claim 49 , wherein the first processing circuitry and the second processing circuitry define a microprocessor.  
     
     
         58 . The system of  claim 49 , wherein the first processing circuitry and the second processing circuitry define a firmware.  
     
     
         59 . The system of  claim 49 , wherein the sample spectrum is one of a Raman spectrum, near infrared absorption/reflectance spectrum, infrared absorption/reflectance spectrum visible absorption/reflectance spectrum or fluorescence spectrum.  
     
     
         60 . The system of  claim 49 , wherein the calibrant is selected from the group consisting of acetaminophen, polymethyl methacrylate, oxygen and nitrogen, neon, krypton, xenon, BK-7 glass, quartz, fused silica, naphthalene, 1,4 bis(2-methylstyryl)benzene, sulfur, toluene, acetonitrile, benzonitrile, cyclohexane, polystyrene, dysprosium oxide, and holmium oxide.  
     
     
         61 . The system of  claim 49 , wherein the spectrograph is a spectrometer.  
     
     
         62 . The system of  claim 49 , wherein the plurality of illuminating photons have a first wavelength.  
     
     
         63 . The system of  claim 49 , further comprising an optical filter for separating the first plurality of photons from the second plurality of photons.  
     
     
         64 . The system of  claim 49 , wherein the optical train further comprises an optical filter for separating the first plurality of photons from the second plurality of photons.  
     
     
         65 . The system of  claim 49 , wherein the intrinsic calibrant is coated on a portion of the optical train interposed in the first optical path.