Terahertz imaging system performance model for concealed weapon identification

Murrill, Steven R.; Jacobs, Eddie L.; Moyer, Steven K.; Halford, Carl E.; Griffin, Steven T.; Lucia, Frank C. De; Petkie, Douglas T.; Franck, Charmaine C.

doi:10.1117/12.630877

Cited by 7 publications

(6 citation statements)

References 6 publications

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“…It has been shown that commonly used explosives have a number of spectral features in the THz region, which can be used to identify the explosive, [8,13,14,16,32,34,35] even if concealed behind optically opaque materials. [10,36,37] It has also been shown that a range of plasticisers and dyes used in the manufacture of explosives are transparent in the terahertz region and thus identification of the explosive in these complex mixtures remains possible. [16] Although spectral features of a large range of explosives have been identified, it is only recently that the origin of these modes has been ascribed and predicted accurately, using theoretical calculations.…”

Section: Introductionmentioning

confidence: 99%

Calculation and Measurement of Terahertz Active Normal Modes in Crystalline PETN

Burnett¹,

Kendrick²,

Cunningham³

et al. 2010

ChemPhysChem

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Section: Introductionmentioning

confidence: 99%

Calculation and Measurement of Terahertz Active Normal Modes in Crystalline PETN

Burnett¹,

Kendrick²,

Cunningham³

et al. 2010

ChemPhysChem

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“…This comparison of ZBD versus pyroelectric detector response was used to fit to a second order polynomial and then used to linearize the measured ZBD power. The scattered power levels on the ZBD were typically more than 40 dB lower than the source power, well into the ZBD linear regime, but the linearization was necessary to properly establish the incident power on the target, P i of Equation 1. Compression (saturation) in the ZBD response led to about a 2 dB correction in P i .…”

Section: Instrument Designmentioning

confidence: 98%

“…The bidirectional scattering distribution function (BSDF) and the area normalized bidirectional radar cross section (σº) are related concepts and are needed to determine detection threshold levels in radars and other active imagers [1,9]. Since our measurement geometry is reflective, BSDF is equivalent to bidirectional reflectance distribution function (BRDF).…”

Section: Introductionmentioning

confidence: 99%

“…Since our measurement geometry is reflective, BSDF is equivalent to bidirectional reflectance distribution function (BRDF). The cosine corrected BSDF is [2] BSDF = i s s P P Ω / (1) where P s is the power scattered into a detector with angular aperture subtending Ω s steradians from the point of view of the scattering target surface, and P i is total power incident onto the target surface.…”

Section: Introductionmentioning

confidence: 99%

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650 GHz bistatic scattering measurements on human skin

2014

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Many groups are developing submillimeter cameras that will be used to screen human subjects for improvised explosive devices (IEDs) and other threat items hidden beneath their clothing. To interpret submillimeter camera images the scattering properties, specifically the bidirectional scattering distribution function (BSDF) must be known. This problem is not trivial because surfaces of man-made objects and human skin have topographic features comparable to the wavelength of submillimeter radiation -thus simple, theoretical scattering approximations do not apply. To address this problem we built a goniometer instrument to measure the BSDF from skin surfaces of live human subjects illuminated with a beam from a 650 GHz synthesized source.To obtain some multi-spectral information, the instrument was reconfigured with a 160 GHz source. Skin areas sampled are from the hand, interior of the forearm, abdomen, and back. The 650 GHz beam has an approximately Gaussian profile with a FWHM of approximately 1 cm. Instrument characteristics: angular resolution 2.9º; noise floor -45 dB/sr; dynamic range > 70 dB; either s or ppolarization; 25º ≤ bidirectional-scattering-angle ≤ 180º; The human scattering target skin area was placed exactly on the goniometer center of rotation with normal angle of incidence to the source beam. Scattering power increased at the higher frequency. This new work enables radiometrically correct models of humans.

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“…Murrill et al, has adapted the latest U.S. Army NVESD sensor model to accommodate THz imaging 3 . A defined target set consisting of small handheld weapons was blurred in a known fashion and then used in a perception experiment to determine task difficulty (V 50 ) for the soldier.…”

Section: Introductionmentioning

confidence: 99%

Terahertz standoff imaging testbed design and performance for concealed weapon and device identification model development

Franck

Lee²,

Espinola

et al. 2007

SPIE Proceedings

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This paper describes the design and performance of the U.S. Army RDECOM CERDEC Night Vision and Electronic Sensors Directorate's (NVESD), active 0.640-THz imaging testbed, developed in support of the Defense Advanced Research Project Agency's (DARPA) Terahertz Imaging Focal-Plane Technology (TIFT) program. The laboratory measurements and standoff images were acquired during the development of a NVESD and Army Research Laboratory terahertz imaging performance model. The imaging testbed is based on a 12-inch-diameter Off-Axis Elliptical (OAE) mirror designed with one focal length at 1 m and the other at 10 m. This paper will describe the design considerations of the OAE-mirror, dual-capability, active imaging testbed, as well as measurement/imaging results used to further develop the model. INTRODUCTIONIn recent years, research has advanced terahertz technology to the point of being a potential solution for identifying weapons through clothing 1-2 . While millimeter-wave imaging has demonstrated very effective imaging in fog and dust, THz technology offers higher resolution for a given aperture size, and also provides penetration of a variety of nonconducting materials at significant standoff distances. This paper will discuss the rationale behind the design of a 12-inch-diameter, OAE-mirror-based testbed, the data acquisition methodology and set-up of the Virginia Diodes, Inc. (VDI) 0.640 THz source and heterodyne receiver components, and will present a preliminary implementation of the latest DARPA TIFT THz Imaging System Performance Analysis Model (Alpha Plus) that is currently in development. BACKGROUNDThe U.S. Army NVESD has over fifty years of experience in developing sensor-based models. NVESD and the U.S. Army Research Laboratory (ARL-SEDD and ARL-CISD) have partnered with Ohio State University (OSU), Wright State University (WSU), and University of Memphis (U of M), under the DARPA TIFT program, in the development of a terahertz-band imaging system performance analysis model. Jacobs et al., has outlined the methodology, as well as, radiometric and human-visual-system-response considerations for extending the U.S. Army target acquisition models to THz imaging for the task of concealed weapon identification 1 . In 2005 Petkie et al., successfully developed millimeter/submillimeter/terahertz systems that could be configured to study both active (0.640-THz source and heterodyne receiver) and passive imaging (bolometric detector), transmission and scattering measurements for common clothing, and associated phenomenology 2 . The imaging studies were based on a 12-inch, raster-scanned mirror system designed and built at OSU.Murrill et al., has adapted the latest U.S. Army NVESD sensor model to accommodate THz imaging 3 . A defined target set consisting of small handheld weapons was blurred in a known fashion and then used in a perception experiment to

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Terahertz imaging system performance model for concealed weapon identification

Cited by 7 publications

References 6 publications

Calculation and Measurement of Terahertz Active Normal Modes in Crystalline PETN

Calculation and Measurement of Terahertz Active Normal Modes in Crystalline PETN

650 GHz bistatic scattering measurements on human skin

Terahertz standoff imaging testbed design and performance for concealed weapon and device identification model development

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