Patent US5835213A successfully refreshed from Google Patents.
US5835213A
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Triple modulation experiment for a fourier transform spectrometer
Assignee: Agilent Technologies Australia M Pty Ltd
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Filing: 1996-09-13
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Granted: 1998-11-10
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Expires: 2016-09-13
Abstract
Abstract For a step-scanning Fourier transform spectrometer comprising an interferometer, a detector, and a digital signal processor (DSP), a method for measuring a response of a sample to multiple modulations is disclosed. In one embodiment, the method comprises the steps of utilizing the DSP to measure a phase modulation angle and a sample modulation angle; obtain an interferogram that corresponds to a calibrated static sample response by using the measured phase modulation rotation angle; obtain another interferogram which corresponds to the calibrated dynamic sample response by using both the measured phase and sample modulation rotation angles; and computing one or more spectra from the interferograms which indicates the calibrated response of said sample to the multiple modulations.
Inventors
- 👤 Raul Curbelo
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 20:49
CPC Classifications
G; G01; G01J; G01J3/00; G01J3/28; G01J3/45; G01J3/453; G01J2003/2866
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
212 words
In a step-scanning Fourier transform spectrometer comprising an interferometer, a detector, and a digital signal processor (DSP), a method for measuring a spectral response of a sample-under-test to multiple modulations, including a phase modulation and a sample modulation, said method comprising the steps of: measuring, using the DSP, a phase modulation signal delay for the Fourier transform spectrometer; and measuring, using the DSP, a sample modulation signal delay for said Fourier transform spectrometer; obtaining a first interferogram, I(k), representing a response of the sample-under-test to the phase modulation, wherein said first interferogram is corrected for said phase modulation signal delay; obtaining a second interferogram, ID I(k), representing an in-phase component of a response of the sample-under-test to the phase modulation and the sample modulation, wherein said second interferogram is corrected for said phase modulation signal delay and said sample modulation signal delay; obtaining a third interferogram, ID Q(k), representing a quadrature component of a response of the sample-under test to the phase modulation and the sample modulation, wherein said third interferogram is corrected for said phase modulation signal delay and said sample modulation signal delay; and computing one or more spectra from said first, second and third interferograms, said spectra representing the calibrated spectral response of the sample to the multiple modulations.
Claim 2
Dependent Claim
212 words
In a step-scanning Fourier transform spectrometer comprising an interferometer, a detector, and a digital signal processor (DSP), a method for measuring a spectral response of a sample-under-test to multiple modulations, including a phase modulation and a sample modulation, said method comprising the steps of: measuring, using the DSP, a phase modulation signal delay for the Fourier transform spectrometer; and measuring, using the DSP, a sample modulation signal delay for said Fourier transform spectrometer; obtaining a first interferogram, I(k), representing a response of the sample-under-test to the phase modulation, wherein said first interferogram is corrected for said phase modulation signal delay; obtaining a second interferogram, ID I(k), representing an in-phase component of a response of the sample-under-test to the phase modulation and the sample modulation, wherein said second interferogram is corrected for said phase modulation signal delay and said sample modulation signal delay; obtaining a third interferogram, ID Q(k), representing a quadrature component of a response of the sample-under test to the phase modulation and the sample modulation, wherein said third interferogram is corrected for said phase modulation signal delay and said sample modulation signal delay; and computing one or more spectra from said first, second and third interferograms, said spectra representing the calibrated spectral response of the sample to the multiple modulations.
Claim 3
Dependent Claim
124 words
The method of claim 1, wherein said step of measuring a phase modulation signal delay comprises the sub-steps of: replacing said sample-under-test with a sample producing no additional phase modulation signal delay over a frequency band of interest; obtaining a first cosine interferogram and a first sine interferogram from the spectrometer representing a response of the spectrometer to the phase modulation signal and including the phase modulation signal delay; identifying a peak of said first cosine and sine interferograms and assuming that said peak is near a point of stationary phase; finding an phase modulation delay angle, Θφo, for which a linear orthogonal transformation of said first cosine and sine interferograms brings to zero the area under a quadrature component of a corresponding spectrum.
Claim 4
Dependent Claim
128 words
The method of claim 2, wherein said step of measuring a sample modulation signal delay comprises the steps of: replacing said sample-under-test with a sample producing no additional sample modulation signal delay; obtaining a second cosine interferogram and a second sine interferogram from the spectrometer representing a response of the spectrometer to the phase modulation and to the sample modulation and including said phase modulation signal delay and said sample modulation signal delay; identifying a peak of said second cosine and sine interferograms and assuming that said peak is near a point of stationary phase; finding a sample modulation delay angle, Θso, for which a linear orthogonal transformation of said second cosine and sine interferograms brings to zero the area under a quadrature component of a corresponding spectrum.
Claim 5
Dependent Claim
174 words
The method of claim 3, wherein said step of finding a phase modulation delay angle comprises the sub-steps of: finding a first angle, Θφ, for which a linear orthogonal transformation of said first cosine and sine interferograms measured at an index corresponding to said peak provides a rotated sine component which is zero and a rotated cosine component which is greater than zero; performing, using said first angle, a linear orthogonal transformation on said first cosine and sine interferograms to provide a rotated cosine interferogram and a rotated sine interferogram; computing an in-phase spectrum and a quadrature spectrum from said rotated cosine interferogram and said rotated sine interferogram, respectively; calculating an in-phase spectrum area and a quadrature spectrum area from said in-phase spectrum and said quadrature spectrum, respectively; finding a second angle, Θφ1, for which a linear orthogonal transformation of said in-phase spectrum area and said quadrature spectrum area brings to zero the area under a rotated quadrature spectrum; combining said first angle and said second angle to produce said phase modulation delay angle.
Claim 6
Dependent Claim
174 words
The method of claim 3, wherein said step of finding a sample modulation delay angle comprises the sub-steps of: finding a first angle, Θs, for which a linear orthogonal transformation of said second cosine and sine interferograms measured at an index corresponding to said peak provides a rotated sine component which is zero and a rotated cosine component which is greater than zero; performing, using said first angle, a linear orthogonal transformation on said second cosine and sine interferograms to provide a rotated cosine interferogram and a rotated sine interferogram; computing an in-phase spectrum and a quadrature spectrum from said rotated cosine interferogram and said rotated sine interferogram, respectively; calculating an in-phase spectrum area and a quadrature spectrum area from said in-phase spectrum and said quadrature spectrum, respectively; finding a second angle, Θs1, for which a linear orthogonal transformation of said in-phase spectrum area and said quadrature spectrum area brings to zero the area under a rotated quadrature spectrum; combining said first angle and said second angle to produce a sample modulation delay angle.
Claim 7
Dependent Claim
130 words
The method of claim 2, wherein said step of measuring a sample modulation signal delay comprises the steps of: replacing said sample-under-test with a sample producing no additional sample modulation signal delay; obtaining a second cosine interferogram and a second sine interferogram from the spectrometer representing a response of the spectrometer to the phase modulation and to the sample modulation and including said phase modulation signal delay and said sample modulation signal delay; identifying a peak of said second cosine and sine interferograms and assuming that said peak is near a point of stationary phase; finding a sample modulation delay angle, Θso, for which a linear orthogonal transformation of said second cosine and sine interferograms brings to a minimum a root-mean-square value of a quadrature component of a corresponding spectrum.
Claim 8
Dependent Claim
126 words
The method of claim 1, wherein said step of measuring a phase modulation signal delay comprises the sub-steps of: replacing said sample-under-test with a sample producing no additional phase modulation signal delay over a frequency band of interest; obtaining a first cosine interferogram and a first sine interferogram from the spectrometer representing a response of the spectrometer to the phase modulation signal and including the phase modulation signal delay; identifying a peak of said first cosine and sine interferograms and assuming that said peak is near a point of stationary phase; finding an phase modulation delay angle, Θφo, for which a linear orthogonal transformation of said first cosine and sine interferograms brings to a minimum the root-mean-square value of a quadrature component of a corresponding spectrum.
References Cited (Backward Citations)
US5450196A
Cited
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