Standardizing and calibrating a spectrometric instrument
First Claim
1. A method of standardizing a spectrometric instrument having a characteristic intrinsic profile of spectral line shape for a hypothetically thin spectral line in each segment of a selected spectral range, each intrinsic profile having an associated intrinsic width, the instrument including a line source of at least one narrow spectral line in at least one selected segment of the spectral range, and each narrow spectral line having an associated line width substantially narrower than the intrinsic width for a corresponding selected segment, the method comprising:
- specifying a target profile of spectral line shape for a hypothetically sharp spectral line in each selected segment, initially operating the instrument with the line source to produce a set of profile data for each narrow spectral line such that each set of profile data is representative of the intrinsic profile for a corresponding selected segment, computing a transformation filter for transforming each set of profile data to a corresponding target profile for each selected segment, and saving the transformation filter for future application to sample data.
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Accused Products
Abstract
A spectrometric instrument which exhibits an intrinsic profile for a sharp spectral line produces profile data for narrow spectral lines. The spectral lines are effected with a high finesse etalon of gold coated polymer. A transformation filter is computed for transforming the profile data to a gaussian profile. A wavelength calibration is combined with the filter to effect a correction matrix which is applied to sample data to generate calibrated standardized data. Iteratively a correction matrix is applied to calibration data to generate standardized calibration data which is utilized for the wavelength calibration. Calibration is effected with an optical standard, an interference etalon and a fringe formula. Etalon effective thickness is first estimated and then precisely determined so that fringe peaks calibrate wavelength.
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Citations
51 Claims
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1. A method of standardizing a spectrometric instrument having a characteristic intrinsic profile of spectral line shape for a hypothetically thin spectral line in each segment of a selected spectral range, each intrinsic profile having an associated intrinsic width, the instrument including a line source of at least one narrow spectral line in at least one selected segment of the spectral range, and each narrow spectral line having an associated line width substantially narrower than the intrinsic width for a corresponding selected segment, the method comprising:
specifying a target profile of spectral line shape for a hypothetically sharp spectral line in each selected segment, initially operating the instrument with the line source to produce a set of profile data for each narrow spectral line such that each set of profile data is representative of the intrinsic profile for a corresponding selected segment, computing a transformation filter for transforming each set of profile data to a corresponding target profile for each selected segment, and saving the transformation filter for future application to sample data. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
- 22. A method of establishing a precision wavelength point in a spectrometric instrument including a calibration source of a spectral peak of precisely identified wavelength, the instrument having a nominal calibration of spectral wavelength versus spectral locations in a spectral range, the method comprising operating the instrument with the calibration source to produce calibration data defining a calibration profile representative of the spectral peak, storing the calibration profile, estimating a centroid wavelength of the calibration profile with respect to the spectral locations, reversing the calibration profile about the estimated centroid wavelength to create a reversed profile, adding the calibration profile and the reversed profile to create a combined profile, and fitting the calibration data to the combined profile to determine an offset between the estimated centroid wavelength and the spectral peak, whereby the offset defines a primary peak location with respect to the spectral locations.
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24. A method of precisely calibrating wavelength in a spectrometric instrument having a nominal calibration of spectral wavelength versus spectral locations in a selected spectral range, the instrument including a calibration source of a primary spectral peak of precisely identified wavelength and a multiple source of a multiplicity of secondary peaks spaced across the spectral range each secondary peak having an integer order number identified by correlation function to a peak wavelength in accordance with a correlation constant, the method comprising:
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additionally operating the instrument with the calibration source to produce calibration data representative of the primary spectral peak, and further additionally operating the instrument with the multiple peak source to produce secondary data representative of the multiplicity of secondary peaks; ascertaining from the calibration data a primary peak location with respect to the spectral locations, and further ascertaining from the secondary data a set of secondary peak locations with respect to the spectral locations; estimating with the correlation function the correlation constant in accordance with order number differential for at least two peak wavelengths determined by the nominal calibration; identifying with the correlation function a calibration order number for at least one selected secondary peak located adjacent the primary peak, said identifying being effected in accordance with the estimated correlation constant and a preliminary wavelength determined for the selected secondary peak by th nominal calibration; interpolating from the selected secondary peak a precise relative positioning of the selected secondary peak and the primary peak calculating with the correlation function a precise correlation constant from the calibration order number, the precisely identified wavelength and the relative positioning; and utilizing the precise correlation constant with the correlation function to assign calibrated wavelengths to associated order numbers and thereby to secondary peak locations with respect to the spectra locations. - View Dependent Claims (25, 26, 27, 28, 29)
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30. A spectrometric instrument having a characteristic intrinsic profile for a hypothetically thin spectral line in each segment of a selected spectral range, each intrinsic profile having an associated intrinsic width, the instrument including a line source of at least one narrow spectral line in at least one selected segment of the spectral range, and each narrow spectral line having an associated line width substantially narrower than the intrinsic width for a corresponding selected segment, and the instrument further including a standardizing system comprising:
specifying means for specifying a target profile for a hypothetically thin spectral line in each selected segment, initial means for initially operating the instrument with the line source to produce a set of profile data for each narrow spectral line such that each set of profile data is representative of the intrinsic profile for a corresponding selected segment, computing means for computing a transformation filter for transforming each set of profile data to a corresponding target profile for each selected segment, operating means for normally operating the instrument with a sample source to produce sample data representative of a sample spectrum, and application means for applying the transformation filter to the sample data in each selected segment to generate standardized sample data representative of the sample spectrum. - View Dependent Claims (31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43)
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44. A spectrometric instrument including a calibration source of at least one primary spectral peak of precisely identified wavelength, and a multiple source of a multiplicity of secondary peaks spaced across the spectral range, each secondary peak having an integer order number identified by correlation function to a peak wavelength in accordance with a correlation constant, the instrument having a nominal calibration of spectral wavelength versus spectral locations in a selected spectral range, and the instrument further including calibration means comprising:
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additional means for additionally operating the instrument with the calibration source to produce calibration data representative of the primary spectral peak, and further additionally operating the instrument with the multiple peak source to produce secondary data representative of the multiplicity of secondary peaks; ascertaining means for ascertaining from the calibration data a primary peak location with respect to the spectral locations, and further ascertaining from the secondary data a set of secondary peak locations with respect to the spectra locations; estimating means for estimating with the correlation function the correlation constant in accordance with order number differential for at least two peak wavelengths determined by the nominal calibration; identifying means for identifying with the correlation function a calibration order number for at least one selected secondary peak located adjacent the primary peak, said identifying being effected in accordance with the estimated correlation constant and a preliminary wavelength determined for the selected secondary peak by the nominal calibration; interpolating means for interpolating from the selected secondary peak a precise relative positioning of the selected secondary peak and the primary peak; calculating means for calculating with the correlation function a precise correlation constant from the calibration order number, the precisely identified wavelength and the relative positioning; and utilizing means for utilizing the precise correlation constant with the correlation function to assign calibrated wavelengths to associated order numbers and thereby to secondary peak locations with respect to the spectral locations. - View Dependent Claims (45, 46, 47, 48)
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- 49. An etalon structure including a high finesse etalon for passing near infra-red spectral lines, the etalon comprising a thin polymer film having a semitransparent gold coating on each side thereof, each coating being sufficient to provide between 1% and 10% transmission, the etalon structure further including a pair of planar glass windows with the etalon sandwiched therebetween.
Specification