15 April 2008 Differential spectroscopic imaging of particulate explosives residue
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Abstract
We present experimental results showing transmission and reflection imaging of approximately 100 μg quantities of particulate explosives residue using a commercial uncooled microbolometer infrared camera and CO2 laser differential wavelength illumination. Fine particulates may be generated during bomb-making activities and these particulates can tenaciously adhere to packing material, as well as to the clothing or skin of the bomb maker and could be detectable during transportation. A rapid screening method that detects this residue can serve as a first-line screening method in conjunction with more sensitive, but invasive, approaches. Explosives exhibit absorption features in the mid-infrared molecular fingerprint region that spans 3 to 15 μm, which can be probed with many high-brightness sources such as fixed wavelength and tunable quantum cascade lasers, CO2, CO, and OPO lasers. Commercial uncooled microbolometer cameras typically have detection sensitivity from 7.5 to 13 μm, spanning an absorption region for explosives detection with adequate signal-to-noise ratio. By illuminating a target on and off its absorption wavelengths, ratio images of suspected residue can be obtained without any sample preparation or cooperation and contact with the target. Our proof-of-principle experiment employed tunable CO2 lasers, with a tuning range from 9.2 to 10.6 μm, overlapping minor absorption features of RDX and Tetryl.
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Bruce E. Bernacki, Nicolas Hô, "Differential spectroscopic imaging of particulate explosives residue", Proc. SPIE 6945, Optics and Photonics in Global Homeland Security IV, 694517 (15 April 2008); doi: 10.1117/12.776917; https://doi.org/10.1117/12.776917
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