Explosives detection using optical spectroscopy
First Claim
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−
1;
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−
1 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−
1, 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−
1 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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Abstract
A method for determining whether a sample includes a nitrate-based explosive comprises receiving the sample and selecting an area of interest on the sample. Then, at least a portion of the area of interest is interrogated with an optical source to produce a spectrum with an amplitude. The amplitude of a first portion of the spectrum is compared to a first predetermined threshold to determine if the sample includes a nitrate. After determining that the sample includes a nitrate in the area of interest, the amplitude of a second portion of the spectrum is compared to a second predetermined threshold to determine if the sample includes a secondary indicator. Then, an indicator is activated based on the determinations.
57 Citations
15 Claims
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1. A method for detecting threat materials used in explosives, comprising:
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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−
1;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−
1 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−
1, 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−
1 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; andactivating an indicator if the verification indicates that the sample contains the threat material. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method for detecting threat materials used in explosives, comprising:
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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−
1;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−
1 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 550 cm−
1, 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 urea nitrate by comparing the amplitude of the measured portion of the second Raman spectrum at approximately 550 cm−
1 to the predetermined threshold, where the second threshold is set to a value corresponding to a feature in the second spectral range indicative of urea nitrate; andactivating an indicator if the verification indicates that the sample contains the threat material.
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Specification