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13 October 2011 Near infrared transmission through clothing: applications in sensing and screening
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Experiments have been performed to demonstrate that near infrared (NIR) transmission through a wide range of clothing materials is possible. Studies have shown that the characteristics of NIR transmission are affected by both the type of fibre used, and the weave pattern. A series of experiments has indicated that NIR transmission is also dependent on other variables such as fabric porosity and dye colour. It is shown that, in many cases, transmission coefficients are sufficiently high that imaging and spectroscopy of objects hidden behind clothing samples should be possible. However, while transmission through clothing at NIR wavelengths in the 750-1,700 nm range is often more effective than in the visible or IR regions, the fabrics themselves will modify the transmitted signal in terms of spatial effects, intensity and spectral content. The paper also describes the possible use of near infrared signals to identify objects that are hidden behind clothing layers. This can be done using spectroscopy. It is important, however, to distinguish the various contributions that exist within the backscattered signal. A set of careful laboratory experiments have demonstrated that transmission through a set of different clothing fabrics does modify the spectral content of signals, but that the spectrum of a particular chemical can still be identified, provided certain steps are taken. These involve a set of careful calibration measurements, and the use of processing techniques for the retrieval of data. It will be shown that this is possible for both granular solids and selected liquids.
© (2011) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
D. A. Hutchins, C. M. Canal, A. Saleem, L. A. J. Davis, and R. J. Green "Near infrared transmission through clothing: applications in sensing and screening", Proc. SPIE 8189, Optics and Photonics for Counterterrorism and Crime Fighting VII; Optical Materials in Defence Systems Technology VIII; and Quantum-Physics-based Information Security, 81890K (13 October 2011);

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