Abstract

Phase retrieval from Gabor-type holograms is typically hindered by the twin-image problem, i.e. the problem of separating the phase front from its conjugate [1]. Quantitative shadowgraphy [2,3] is among the methods available for an approximate solution of this problem. Shadowgraphy retrieves the phase map of a propagating wavefront from two snapshots of its transverse intensity profile. However, the method is usually limited by diffraction blurring [2], as it is based on the geometrical optics approximation. Here we present an iterative shadowgraphic method (ISM) which can remove diffraction blurring from shadowgraphically retrieved phase maps [4]. The algorithm calculates iteratively wavefront corrections by solving the Poisson equation with a source term obtained from a reference shadowgram and an artificial shadowgram calculated from the approximated phase map obtained at the previous iteration. Under this aspect, the method merges features from the Gerchberg-Saxton [5] algorithm with those of shadowgraphy.

© 2009 IEEE