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Proceedings Paper

Chemical and explosives point detection through opaque containers using spatially offset Raman spectroscopy (SORS)
Author(s): Paul W. Loeffen; Guy Maskall; Stuart Bonthron; Matthew Bloomfield; Craig Tombling; Pavel Matousek
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Paper Abstract

Spatially Offset Raman Spectroscopy (SORS) is a novel technique used to identify the chemical Raman signature of threat materials within a few seconds through common non-metallic containers, including those containers which may not yield to inspection by conventional backscatter Raman. In particular, some opaque plastic containers and coloured glass bottles can be difficult to analyze using conventional backscatter Raman because the signal from the contents is often overwhelmed by the much stronger Raman signal and/or fluorescence originating from the container itself. SORS overcomes these difficulties and generates clean Raman spectra from both the container and the contents with no prior knowledge of either. This is achieved by making two, or more, Raman measurements at various offsets between the collection and illumination areas, each containing different proportions of the fingerprint signals from the container and content materials. Using scaled subtraction, or multivariate statistical methods, the two orthogonal signals can be separated numerically, thereby providing a clean Raman spectrum of the contents without contamination from the container. Consequently, SORS promises to significantly improve threat detection capability and decrease the falsealarm rate compared with conventional Raman spectroscopy making it considerably more suitable as an alarm resolution methodology (e.g. at airports). In this paper, the technique and method are described and a study of offset value optimization is described illustrating the difference between one and two fixed spatial offsets. It is concluded that two fixed offsets yield an improvement in the SORS measurement which will help maximize the threat detection capability.

Paper Details

Date Published: 3 June 2011
PDF: 9 pages
Proc. SPIE 8018, Chemical, Biological, Radiological, Nuclear, and Explosives (CBRNE) Sensing XII, 80181E (3 June 2011); doi: 10.1117/12.882126
Show Author Affiliations
Paul W. Loeffen, Cobalt Light Systems Ltd. (United Kingdom)
Guy Maskall, Cobalt Light Systems Ltd. (United Kingdom)
Stuart Bonthron, Cobalt Light Systems Ltd. (United Kingdom)
Matthew Bloomfield, Cobalt Light Systems Ltd. (United Kingdom)
Craig Tombling, Cobalt Light Systems Ltd. (United Kingdom)
Pavel Matousek, Cobalt Light Systems Ltd. (United Kingdom)
Rutherford Appleton Lab. (United Kingdom)


Published in SPIE Proceedings Vol. 8018:
Chemical, Biological, Radiological, Nuclear, and Explosives (CBRNE) Sensing XII
Augustus W. Fountain III; Patrick J. Gardner, Editor(s)

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