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Proceedings Paper

Active imaging at 350 GHz for security applications
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Paper Abstract

Imaging in the sub-millimeter wave range of 300 - 1000 GHz is useful for a variety of applications including security screening, imaging through obscurations, and non-destructive evaluation. Waves in this frequency range have wavelengths ranging from 0.3 to 1.0 mm and are able to penetrate many optical obscurants. The ability to form high-resolution images that penetrate clothing makes imaging in this frequency range particularly interesting for personnel security screening at standoff distances. The Pacific Northwest National Laboratory (PNNL) has previously developed portal screening systems that operate at the lower end of the millimeter-wave frequency range around 30 GHz. These systems are well suited for screening within portals and can achieve resolution of about 5 mm at ranges of less than 1 meter. However, increasing the range of these systems would dramatically reduce the resolution due to diffraction at their relatively long wavelength. Operation at much higher frequencies, for example 350 GHz, will enable an order of magnitude improvement of the resolution at a given range, while still achieving adequate clothing penetration. PNNL's portal imaging systems have relied on wavefront reconstruction, or holographic, imaging techniques to mathematically focus the imagery. In the sub-millimeter-wave, this may not always be practical due to sensitivity of the system to slight changes in the position of the imaging target during data collection. In this case, physical focusing using lenses or reflectors may be more practical. In this paper, we examine the effectiveness of imaging near 350 GHz for security screening applications. Imaging results are presented using the holographic wavefront reconstruction technique, as well as a focused reflector-based imaging system.

Paper Details

Date Published: 22 April 2008
PDF: 10 pages
Proc. SPIE 6948, Passive Millimeter-Wave Imaging Technology XI, 69480M (22 April 2008); doi: 10.1117/12.778011
Show Author Affiliations
David M. Sheen, U.S. Department of Energy (United States)
Douglas L. McMakin, U.S. Department of Energy (United States)
Jeffrey Barber, Battelle Memorial Institute (United States)
Thomas E. Hall, U.S. Department of Energy (United States)
Ronald H. Severtsen, U.S. Department of Energy (United States)

Published in SPIE Proceedings Vol. 6948:
Passive Millimeter-Wave Imaging Technology XI
Roger Appleby; David A. Wikner, Editor(s)

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