Nonlinear acoustic concealed weapons detection

The detection of concealed weapons at a distance is a critical security issue that has been a great challenge for different imaging approaches. In this paper, we discuss the use of ultrasonics in a novel way to probe for metallic and nonmetallic materials under clothing. Conventional ultrasonics has problems penetrating clothing and produces false positives from specular reflections. Our approach is to use ultrasonics to create a localized zone where nonlinear interactions generate a lower frequency acoustic wave that is able to penetrate clothing better than direct ultrasonics. The generation of a probing beam for concealed weapons is described in this brief summary showing comparisons of the physical models with the experimental data. An imaging scan of concealed improvised weapons seized by officials at corrections institutes is presented to highlight the value of this approach