650 GHz bistatic scattering measurements on human skin

Abstract

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.

Millimeter wave imaging: a historical review

“…In both cases the results were encouraging but it was clear further work needed to be done. There has now been a great deal of data collection including polarimetric data of scenes [11][12][13] , dust 14 , skin 15 plus many others and our understanding of materials in the millimeter and sub-millimeter wave region has greatly improved. Modeling has also improved considerably, benefitting from high power computers and digital cinematography giving rise to realistic models of objects, people and scenes.…”

Simulation Framework for a 3-D High-Resolution Imaging Radar at 300 GHz with a Scattering Model Based on Rendering Techniques

“…Furthermore, increasing attention is being drawn toward the characterization and measurement of bistatic scattering properties of different materials (especially those present in concealed object detection applications) in the submillimeter band [25]- [27]. These studies have targeted the description of such properties in a way particularly suited for later application in BRDF-based simulators [28].…”