The use of the Herglotz Function Method to reconstruct obstacles from realand from synthetic scattering data

We consider the problem of the reconstruction of the shape of an obstacle f rom some knowledge of the scattered waves generated from the interaction of the obstacle with known incident waves. More precisely we study this inver se scattering problem considering acoustic waves or electromagnetic waves. In both cases the waves are assumed harmonic in time. The obstacle is assum ed cylindrically symmetric and some special incident waves are considered. This allows us to formulate the two scattering problems, i.e. the acoustic scattering problem and the electromagnetic scattering problem, as a boundar y value problem for the scalar Helmholtz equation in two independent variab les. The numerical algorithms proposed are based on the Herglotz Function M ethod, which has been introduced by Colton and Monk.(1) We report the resul ts obtained with these algorithms in the reconstruction of simple obstacles with Lipschitz boundary using experimental electromagnetic scattering data , that is the Ipswich Data(2,3) and in the reconstruction of "multiscale ob stacles" using synthetic acoustic scattering data.