We have recently conducted a series of laboratory and field tests to demonstrate the utility of combining active illumination with hyperspectral imaging for the detection of concealed targets in natural terrain. The active illuminator, developed at MIT Lincoln Laboratory, is a novel microlaser-pumped fiber Raman source that provides high-brightness, subnanosecond-pulse-length output spanning the visible through near-infrared spectral range. The hyperspectral-imaging system is comprised of a compact, grating-based spectrometer that uses a gateable, intensified CCD array as the detector element. The illuminator and hyperspectral imaging system are mounted on a small platform that is itself mounted on a tripod and scanned in azimuth to build an image scene of up to several hundred spectral bands. The system has been deployed under a variety of environmental conditions, including night-time illumination, and on a variety of target scenes, including exposed and concealed plastic and metallic mine-like targets. Targets have been detected and identified on the basis of spectral reflectance, fluorescence signatures, degree of polarization, and range-to-target information (via range gating). The combination of laser-like; broadband illumination and hyperspectral imaging offers great promise in concealed or obscured target detection. Ongoing developments include the incorporation of broadband illuminators in the 1 to 2 mu m and 3 to 5 mu m spectral bands, with corresponding increases in spectral coverage of the imaging and detection systems.
