Scanning spectroscopy modulation for frequency domain spectral analysis
AssigneeThe United States of America as represented by the Secretary of the Navy
InventorsMark Fralick, Richard Waters
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Abstract
A method for analyzing an optical signal comprising: directing the optical signal into a scanning spectrometer system comprising a variable-wavelength filter and a detector; continuously modulating the variable-wavelength filter at a given modulation frequency to produce a time-based waveform; measuring the time-based waveform with the detector; converting the time-based waveform into a frequency spectrum comprising harmonics of the modulation frequency; and comparing the harmonics of the modulation frequency to premeasured harmonic spectra in a reference database.
Claims20
A method for analyzing an optical signal comprising:
- directing the optical signal into a scanning spectrometer system comprising a variable-wavelength filter and a detector;
- continuously modulating the variable-wavelength filter at a given modulation frequency to produce a time-based waveform over multiple modulation cycles;
- measuring the time-based waveform with the detector;
- converting the time-based waveform into a frequency spectrum comprising harmonics of the modulation frequency;
- and
- comparing the harmonics of the modulation frequency to premeasured harmonic spectra in a reference database.
A method for analyzing a Raman or Surface Enhanced Raman Spectroscopy (SERS) emission from a sample comprising:
- directing the emission into a resonant cavity of a Fabry-Perot interferometer, wherein the resonant cavity comprises first and second mirrors;
- modulating the position of the first mirror with respect to the second mirror at a given modulation frequency;
- measuring a time-based spectrum over time as a function of first mirror position at a detector over multiple modulation cycles;
- taking a Fourier Transform of the time-based spectrum to obtain a frequency-based spectrum centered around the modulation frequency;
- determining information about the shape of the time-based spectrum based on the phase and amplitude of the harmonics of the modulation frequency;
- comparing the information to premeasured harmonic spectra in a reference database;
- and
- establishing the presence of chemical or biological agents within the sample, by discriminating distinguishing components of each agent within the frequency-based spectrum.
Dependencies are inferred from the claim text.