  We are interested in the localization of defects in non-absorbing
inhomogeneous media with far-field measurements generated by plane waves. In
localization problems, most so-called sampling methods are based on a
characterization involving point-sources and the range of some implicitly
defined operator. We present here a way to deal with this implicit operator by
the means of an optimization approach in the lines of the well-known inf
criterion for the factorization method.
