Quantitative inversion of complex contrasts with the finite-difference contrast source inversion method

This paper presents a finite-difference based CSI (FD-CSI) algorithm for solving the electromagnetic inverse problem. In contrast to the usual CSI method, the algorithm is based on a FD method, which allows for the inclusion of inhomogeneous backgrounds throughout the inversion process. Through a numerical example, it is shown that when accurate a-priori information about the scatterer is known, the use of this information as a background throughout the inversion process provides improved inversion results over the case where the a-priori information is used as an initial guess. The algorithm is presented for the two-dimensional (2D) TM inverse problem, but the algorithm is extendable to the full-vector three-dimensional (3D) inverse problem.