Abstract: Apparatus that invention detects and characterizes hard or metallic materials or objects, worn or carried by persons or concealed on their persons or in bags or luggage, using directed or propagated energy such as ultrasound or microwave, that is reflected or scattered by the materials and objects of interest and that has a wavelength or wavelengths such that the width and/or shape of the reflected beam can be measured at the desired detection distance or range of distances and has a measurable dependence on the size and/or shape of the object, utilizing diffraction methods. Also disclosed are a system and a method utilizing this apparatus.

Abstract: Embodiments of this invention utilize Fraunhofer diffraction to detect, locate, and characterize buried objects, and, in particular, weapons caches and/or potentially dangerous explosive devices, are to be detected and characterized according to rough size, shape, and reflectivity with respect to the probe energy (ultrasound, microwave, milliwave, etc.). Size is obtained by measuring the spatial pattern and/or width of the Fraunhofer diffraction wave. Reflectivity is obtained by normalizing the reflected energy with respect to the energy reaching the target object and the size of the reflective area of the target object.