Methods for collection, dark correction, and reporting of spectra from array detector spectrometers

Abstract

Methods and systems for spectrometer dark correction are described which achieve more stable baselines, especially towards the edges where intensity correction magnifies any non-zero results of dark subtraction, and changes in dark current due to changes in temperature of the camera window frame are typically more pronounced. The resulting induced curvature of the baseline makes quantitation difficult in these regions. Use of the invention may provide metrics for the identification of system failure states such as loss of camera vacuum seal, drift in the temperature stabilization, and light leaks. In system aspects of the invention, a processor receives signals from a light detector in the spectrometer and executes software programs to calculate spectral responses, sum or average results, and perform other operations necessary to carry out the disclosed methods. In most preferred embodiments, the light signals received from a sample are used for Raman analysis.

1 . A method of dark current correction in a spectrometer having a detector adapted to receive a light spectrum from a sample, the method comprising the steps of:
 (a) acquiring a dark exposure using the detector;   (b) acquiring a light exposure from a sample;   (c) subtracting the dark exposure from the light exposures, storing the result as an accumulation;   (d) repeating (a)-(c) for N accumulations; and   (e) summing or averaging the N accumulations to generate a result.   
     
     
         2 . The method of  claim 1 , wherein the spectra acquired in (a) and (b) are cosmically corrected. 
     
     
         3 . The method of  claim 1 , wherein the spectrometer is a Raman spectrometer, and the light spectrum from the sample includes a Raman spectrum. 
     
     
         4 . The method of  claim 1 , including the steps of:
 (a) acquiring a dark exposure using the detector;   (b) acquiring a light exposure from a sample;   (c) subtracting the dark exposure from the light exposures, storing the result in a buffer as an accumulation;   (d) repeating (a)-(c) for N accumulations;   (e) summing or averaging the N accumulations to generate a result;   (f) deleting the oldest element in the buffer; and   (g) repeating steps (a) through (f) until a desired number of spectra have been collected.   
     
     
         5 . The method of  claim 4 , wherein the spectrometer is a Raman spectrometer, and the light spectrum from the sample includes a Raman spectrum. 
     
     
         6 . A method of dark current correction in a spectrometer having a detector with a illuminated area adapted to receive light from a sample and a non-illuminated area, the method comprising the steps of:
 (a) receiving and storing data representative of a true dark (TD) spectrum using the illuminated area of the detector in the absence of light from the sample, and receiving and storing data representative of an unilluminated dark (UD) spectrum using the non-illuminated area of the detector in the presence of light from the sample;   (b) deriving a mathematical relationship between TD and UD;   (c) simultaneously receiving and storing data representative of a light spectrum from a sample using the illuminated area of the detector, and receiving and a new unilluminated dark (new UD) spectrum using the non-illuminated area of the detector;   (d) calculating a new TD as a function of new UD;   (e) subtracting new TD from the data representative of the light spectrum to generate a result; and   (f) repeating steps (c) through (e) until a desired number of spectra have been collected.   
     
     
         7 . The method of  claim 6 , wherein the spectrometer is a Raman spectrometer, and the light spectrum from the sample includes a Raman spectrum. 
     
     
         8 . The method of  claim 6 , including the steps of:
 storing the result of step (e) in a buffer;   repeating steps (c) through (e) until the buffer is full, then:
 (g) summing or averaging the elements of the buffer; 
 (h) generating a result; 
 (i) deleting the oldest element in the buffer; and 
 (j) repeating steps (c) through (i) until a desired number of spectra have been collected. 
   
     
     
         9 . The method of  claim 8 , wherein the spectrometer is a Raman spectrometer, and the light spectrum from the sample includes a Raman spectrum. 
     
     
         10 . A method of dark current correction in a spectrometer having a detector adapted to receive light from a sample, the method comprising the steps of:
 (a) receiving and storing data representative of a dark spectrum acquired by the detector at one or more detector states and detector parameters;   (b) calculating and storing a detector-specific model based on the detector states and detector parameters;   (c) receiving data representative of a sample spectrum, and storing the data along with one or more detector states and detector parameters;   (d) calculating a dark spectral response based on the model stored in (b);   (e) subtracting the calculated dark spectral response from the sample spectrum;   (f) repeating steps (c)-(e) to generate N accumulations, then:   (h) summing/averaging the N accumulations to produce a result.   
     
     
         11 . The method of  claim 10 , wherein the spectrometer is a Raman spectrometer, and the light spectrum from the sample includes a Raman spectrum. 
     
     
         12 . The method of  claim 6 , wherein associated with the detector states or detector parameters includes temperature or exposure time. 
     
     
         13 . A method of dark current correction in a spectrometer having a detector adapted to receive light from a sample, the method comprising the steps of:
 (a) receiving and storing data representative of a dark spectrum acquired by the detector at one or more detector states and detector parameters;   (b) calculating and storing a detector-specific model based on the detector states and detector parameters;   (c) receiving data representative of a sample spectrum, and storing the data along with one or more detector states and detector parameters;   (d) collecting an unilluminated dark (UD) spectrum using a non-collection area of the detector;   (e) establishing SMUD as a function of UD;   (f) receiving data representative of a sample spectrum, and storing the data along with one or more detector states and detector parameters;   (g) calculating a dark spectral response based on SMUD;   (h) comparing the modeled dark and SMUD;   (i) correcting the dark spectral response using the modeled dark and SMUD;   (j) repeating steps (f)-(i) to generate N accumulations, then:   (k) summing/averaging the N accumulations to produce a result.   
     
     
         14 . The method of  claim 13 , wherein the spectrometer is a Raman spectrometer, and the light spectrum from the sample includes a Raman spectrum. 
     
     
         15 . The method of  claim 13 , wherein associated with the detector states or detector parameters includes temperature or exposure time.