UNWRAPPING OF INTERFEROMETRIC PHASE-FRINGE MAPS BY THE DISCRETE COSINE TRANSFORM

Current whole-field interferometric techniques yield a phase distribut ion in module 2 pi. Removal of the resulting cyclic discontinuities is a process known as unwrapping, which must be performed before the dat a can be interpreted. We investigate an iterative unwrapping technique recently published by Ghiglia and Romero [J. Opt. Sec. Am. A 11, 107 (1994)], which is based on least-squares minimization, obtained by the discrete cosine transform. We apply this technique to remove phase wr aps from electronic speckle pattern interferometry data, using modest personal computer hardware. The algorithm is shown to be fast, easy to implement, robust in the presence of noise, and able to handle phase inconsistencies without propagating local errors. (C) 1996 Optical Soc iety of America