Spectral drift and correction technique for hyperspectral imaging systems
First Claim
1. A method for detecting spectral drift in a hyperspectral imaging system, comprising the steps of:
- (a) obtaining in-field measurements of a response function for a calibration filter;
(b) obtaining in-field measurements of a response function for an onboard blackbody;
(c) determining a spectral transmittance function using said response functions from steps (a) and (b) for said calibration filter and said onboard blackbody;
(d) determining a first derivative function of said spectral transmittance function;
(e) separating said first derivative function into a plurality of spectral band regions, each of said spectral band regions having +/−
N pixels on either side of a localized minima;
(f) determining a pixel shift magnitude value for one of said plurality of spectral band regions; and
(g) applying said pixel shift magnitude value to a look-up table to determine a magnitude and direction of said spectral drift for one of said plurality of spectral band regions.
1 Assignment
0 Petitions
Accused Products
Abstract
A method for determining magnitude and direction of spectral channel drift for several consecutive spectral regions over a wide spectral range. According to the method of the present invention, in-field testing of a spectral filter sequentially irradiated by two blackbody sources is performed to generate a response function of the spectral filter. The response function is ensemble averaged to reduce any noise. Background radiance is then removed to produce a smoothed spectral transmittance function of the spectral filter. The first derivative function of the smoothed spectral transmittance function is determined. The first derivative function is separated into spectral band regions having +/− N pixels on either side of the function minima. The value of N is selected to optimize the detection algorithm sensitivity to change while extending the limit of spectral shift magnitude. The sum of the differences between the first derivative function and a reference spectral derivative function is determined. The difference result is applied to a look-up table to determine magnitude and direction of spectral drift for each of the separated spectral band regions. Use of the present invention can provide information on spectral distortion or spectral smile for 2-D focal plane arrays used for hyperspectral imaging.
-
Citations
38 Claims
-
1. A method for detecting spectral drift in a hyperspectral imaging system, comprising the steps of:
-
(a) obtaining in-field measurements of a response function for a calibration filter;
(b) obtaining in-field measurements of a response function for an onboard blackbody;
(c) determining a spectral transmittance function using said response functions from steps (a) and (b) for said calibration filter and said onboard blackbody;
(d) determining a first derivative function of said spectral transmittance function;
(e) separating said first derivative function into a plurality of spectral band regions, each of said spectral band regions having +/−
N pixels on either side of a localized minima;
(f) determining a pixel shift magnitude value for one of said plurality of spectral band regions; and
(g) applying said pixel shift magnitude value to a look-up table to determine a magnitude and direction of said spectral drift for one of said plurality of spectral band regions. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
-
-
20. A computer program product comprising a computer useable medium having computer program logic recorded thereon for enabling a computer to detect spectral drift in a hyperspectral imaging system, said computer program logic comprising:
-
means for enabling a processor to obtain in-field measurements of a response function for a calibration filter;
means for enabling a processor to obtain in-field measurements of a response function for an onboard blackbody;
means for enabling a processor to determine a spectral transmittance function using said response functions for said calibration filter and said onboard blackbody;
means for enabling a processor to determine a first derivative function of said spectral transmittance function;
means for enabling a processor to separate said first derivative function into a plurality of spectral band regions, each of said spectral band regions having +/−
N pixels on either side of a localized minima;
means for enabling a processor to determine a pixel shift magnitude value for one of said plurality of spectral band regions; and
means for enabling a processor to apply said pixel shift magnitude value to a look-up table to determine a magnitude and direction of said spectral drift for one of said plurality of spectral band regions. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38)
-
Specification