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Explosives detection using optical spectroscopy

  • US 9,983,138 B2
  • Filed: 10/13/2016
  • Issued: 05/29/2018
  • Est. Priority Date: 04/17/2014
  • Status: Active Grant
First Claim
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1. A method for detecting threat materials used in explosives, comprising:

  • receiving a sample;

    selecting an area of interest on the sample suspected of containing a threat material indicative of an explosive;

    predetermining that the threat material is a nitrate;

    interrogating, with an optical source, the area of interest by interrogating at least a portion of the area of interest with a Raman laser to produce a first Raman spectrum, wherein the first Raman spectrum is measured in a first spectral region, which is set to a wave number shift around 1050 cm

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    ;

    determining whether the area of interest includes the threat material by comparing an amplitude of a first spectral region measured during the interrogation, to a first predetermined threshold by comparing the amplitude of the measured portion of the first Raman spectrum at approximately 1050 cm

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    to the predetermined threshold, where the predetermined threshold is set to a value corresponding to a feature in the first spectral range that is indicative of a nitrate;

    performing a verification, if the determination indicates that the area of interest includes the threat material, by checking for a secondary indicator of the presence of the threat material by interrogating at least a portion of the area of interest with a Raman laser to produce a second Raman spectrum, wherein the second Raman spectrum is measured in the second spectral region, which is set to a wave number shift around 3225 cm

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    , where the verification is performed by comparing an amplitude of a second spectral region different from the first spectral region, measured during the interrogation, to a second predetermined threshold by determining if the sample includes ammonium nitrate by comparing the amplitude of the measured portion of the second Raman spectrum at approximately 3225 cm

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    to the predetermined threshold, where the second threshold is set to a value corresponding to a feature in the second spectral range indicative of ammonium nitrate; and

    activating an indicator if the verification indicates that the sample contains the threat material.

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