An imaging method for concealed targets

A novel microwave imaging method to detect and possibly characterize nonaccessible targets concealed into a wall or a floor from the measured backscattered field is proposed. The problem is cast as an inverse scattering one aimed at imaging a piecewise homogeneous target embedded in a layered structure. The proposed method is based on a linear sampling method (LSM), a general and computationally effective shape-reconstruction approach that determines the targets morphology through an indicator defined as the regularized solution of a linear inverse problem. However, LSM cannot discern between homogeneous and inhomogeneous targets; hence, it may retrieve the cache but not characterize its content. To overcome this drawback, we propose a two-step approach in which the cache is first imaged by using the standard LSM indicator. Then, by taking advantage of the physical interpretation of the LSM and of the first step's result, a modified indicator is defined and exploited to detect the inclusions possibly hidden in the retrieved cache. Numerical examples are provided as a proof of concept.