Spectroscopic analysis

Abstract

A method and analyser for identifying or verifying or otherwise characterising a sample comprising: using or having an electromagnetic radiation source for emitting electromagnetic radiation in at least one beam at a sample, the electromagnetic radiation comprising at least two different wavelengths, using or having a sample detector that detects affected electromagnetic radiation resulting from the emitted electromagnetic radiation affected by the sample and provides output representing the detected affected radiation, and using or having a processor for determining sample coefficients from the output, and identifying or verifying or otherwise characterising the sample using the sample coefficients and training coefficients determined from training samples, wherein the coefficients reduce sensitivity to a sample retainer variation and/or are independent of concentration.

1 . An analyser for identifying or verifying or otherwise characterising a sample comprising:
 an electromagnetic radiation source for emitting electromagnetic radiation in at least one beam at a sample, the electromagnetic radiation comprising at least two different wavelengths,   a sample detector that detects affected electromagnetic radiation resulting from the emitted electromagnetic radiation affected by the sample and provides output representing the detected affected radiation, and   a processor for determining sample coefficients from the output, and identifying or verifying or otherwise characterising the sample using the sample coefficients and training coefficients determined from training samples.   
     
     
         2 . An analyser according to  claim 1 , wherein the sample detector output represents intensities detected by the detector at the at least two wavelengths, and wherein determining the sample coefficients comprises determining and using a fractional spectral intensity at each wavelength. 
     
     
         3 . An analyser according to  claim 2 , further comprising a reference detector for detecting reference electromagnetic radiation at the at least two wavelengths that provides output representing intensities detected at the at least two wavelengths, and the fractional spectral intensity at each wavelength is a normalised fractional spectral intensity using the output from the reference detector. 
     
     
         4 . A analyser according to  claim 3 , wherein the analyser is used on a plurality of training samples to obtain from the sample detector training output for a plurality of training samples representing intensities detected by the detector at the at least two wavelengths, and wherein the processor is configured to determine the training coefficients by determining and using a fractional spectral intensity at each wavelength of the training output. 
     
     
         5 . An analyser according to  claim 4 , wherein the fractional spectral intensity is a normalised fractional spectral intensity using output from a reference detector. 
     
     
         6 . An analyser according to  claim 5 , wherein the fractional intensity is defined as the proportion of transmitted light measured at a wavelength referenced to the sum of intensities over all the at least two wavelengths. 
     
     
         7 . A method for identifying or verifying or otherwise characterising a sample comprising:
 emitting electromagnetic radiation in at least one beam at a sample, the electromagnetic radiation comprising at least two different wavelengths,   detecting affected electromagnetic radiation resulting from the emitted electromagnetic radiation affected by the sample and providing detected output representing the detected affected radiation,   determining sample coefficients from the output, and identifying or verifying or otherwise characterising the sample using the sample coefficients and training coefficients determined from training samples.   
     
     
         8 . A method according to  claim 7 , wherein the detected output represents intensities detected at the at least two wavelengths, and wherein determining the sample coefficients comprises determining and using a fractional spectral intensity at each wavelength. 
     
     
         9 . A method according to  claim 8 , further comprising detecting reference electromagnetic radiation at the at least two wavelengths and providing output representing intensities detected at the at least two wavelengths, and the fractional spectral intensity at each wavelength is a normalised fractional spectral intensity using the output from the reference detector. 
     
     
         10 . A method according to  claim 9 , further comprising:
 for a plurality of training samples, emitting electromagnetic radiation in at least one beam at each training sample, the electromagnetic radiation comprising at least two different wavelengths,   for each training sample, detecting affected electromagnetic radiation resulting from the emitted electromagnetic radiation affected by the sample and providing detected output representing the detected affected radiation,   for each sample, determining training coefficients from the output by determining and using a fractional spectral intensity at each wavelength of the training output.   
     
     
         11 . A method according to  claim 10 , wherein the fractional spectral intensity is a normalised fractional spectral intensity using output from a reference detector. 
     
     
         12 . A method according to  claim 11 , wherein the fractional intensity is defined as the proportion of transmitted light measured at a wavelength referenced to the sum of intensities over all the at least two wavelengths. 
     
     
         13 . A method for identifying or verifying or otherwise characterising a sample comprising:
 emitting electromagnetic radiation in at least one beam at a sample, the electromagnetic radiation comprising at least two different wavelengths,   detecting the emitted electromagnetic radiation at each wavelength and providing detected output representing the emitted electromagnetic radiation being reference intensity detected at each wavelength,   detecting affected electromagnetic radiation resulting from the emitted electromagnetic radiation affected by the sample and providing detected output representing the detected affected radiation being output intensity detected at each wavelength,   measuring the temperature of the sample   determining sample coefficients from the output, and   identifying or verifying or otherwise characterising the sample using the sample coefficients and training coefficients determined from training samples, wherein determining the sample coefficients comprises:   eliminating dark current from the output of the reference and output intensities,   determining fractional spectral intensities from the reference and output intensities,   determining a concentration independent coefficient from the fractional spectral intensities,   
       wherein the training coefficients have be determined from data temperature corrected to the temperature of the sample.