Composite techniques for phase retrieval in the Fresnel region

Abstract

In free-space propagation of optical beams, the linear contribution of the object-plane phase to the intensity distribution in the Fresnel region is described by the Transport of Intensity equation (TIE). In the near-Fresnel region, i.e. where the Fresnel number is larger than unity, the linear term can often be dominant. Therefore in this region the TIE can provide a good initial approximation which can then be refined by other techniques, e.g. by Gerchberg-Saxton-Fienup (GSF) type algorithms. Multigrid methods with the TIE applied on coarser grids and GSF algorithms applied on finer grids are shown to be particularly effective in this context. © 2003 Published by Elsevier Science B.V.