Knowledge based spectrometer

• US 8,203,715 B2
• Filed: 05/14/2009
• Issued: 06/19/2012
• Est. Priority Date: 05/14/2009
• Status: Active Grant

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Robinson, Ian S.
• Primary Examiner(s): Chowdhury, Tarifur
• Assistant Examiner(s): Cook, Jonathon
• Application Number:
  US12/466,161
• Publication Number:
  US 20100290053A1
• Time in Patent Office: 1,132 Days
• Field of Search: 356/451, 25033907-33909, 382/280
• US Class Current: 356/451
• CPC Class Codes: G01J 3/02 Details
• CPC Class Codes: G01J 3/0278 Control or determination of height or angle information for sensors or receivers
• CPC Class Codes: G01J 3/28 Investigating the spectrum using colour filters G01J3/51
• CPC Class Codes: G01J 3/45 Interferometric spectrometry
• CPC Class Codes: G01J 3/4535 Devices with moving mirror G01J3/4532 takes precedence

Abstract

A sensor and method for remotely determining a presence of a particular substance based on spectral data of the particular substance is disclosed. The sensor includes a sampling module configured to detect radiation from a particular substance using an interferometer, wherein the sampling module includes a control module that is configured to guide and measure spacing of samples taken by the sampling module; a focal plane module configured to detect and convert an interference pattern produced by the interferometer into a series of digital samples; a reference spectra modification module configured to modify reference spectra by modifying according to the measured spacing of samples and an instrument line shape of the sampling module; an estimation module configured to receive the converted series of digital samples and transform the non-uniformly spaced digital samples into frequency space using band centers determined from reference spectra as modified by the instrument line shape of the sampling module; a comparison module configured to compare the transformed digital samples against a database of known chemical signatures; and a determination module configured to determine the presence of the particular substance based on the results of the comparison.

Claims

1. A method for remotely determining a presence of a particular substance based on spectral data of the particular substance obtained by a spectrometer comprising an interferometer, the method comprising:

using the interferometer to form an interference pattern resulting from an interaction of radiation with the particular substance;

sampling, at the interferometer, the interference pattern to generate a plurality of measured samples having a measured sample spacing associated therewith;

reading reference spectral data from a spectral reference database;

using cosine estimation at the measured sample spacing for determining amplitudes associated with frequencies uniquely associated with features of spectral data in the plurality of measured samples;

modifying the reference spectral data by selecting a plurality of band centers for the reference spectral data;

comparing the modified reference spectral data with the determined spectral data from the cosine estimation; and

determining a presence of the particular substance based on results of the comparing.

2. The method according to claim 1, wherein the particular substance includes chemical elements and molecular compounds.

3. The method according to claim 1, wherein the sampling includes measuring movement of the interferometer by a reference beam.

4. The method according to claim 3, wherein the reference beam is a laser.

5. The method according to claim 3, wherein the measured movement includes a tilt of an optical axis in the interferometer, a modulation in the interference pattern, and a jitter in the interferometer.

6. The method according to claim 5, wherein the modulation is measured as a fringe count of the reference beam.

7. The method according to claim 1, wherein multiple scans are combined with different sample spacings.

8. The method according to claim 1, wherein spectra of received radiation is computed with greater spectral resolution, improved free spectral range and with fewer artifacts.

9. The method according to claim 1, wherein spectra of received radiation is produced without comparisons to a reference spectra.

10. The method according to claim 1, wherein spectra of received radiation is produced from a single scan and/or from multiple scans.

11. The method of claim 1,

wherein the modifying the reference spectral data is based upon the cosine estimation of the plurality of measured samples.

12. The method of claim 1 further comprising:

computing, at the spectrometer, an instrument line shape based on at least one of a tilt, a modulation, and a jitter of the interferometer.

13. The method of claim 1, wherein the using the cosine estimation comprises using at least one of a non-linear least squares analysis and a digital heterodyning technique.