PHASE-CHANGE VISUALIZATION IN 2-DIMENSIONAL PHASE OBJECTS WITH A SEMIDERIVATIVE REAL FILTER

A method of visualization of phase changes in two-dimensional pure-pha se objects by use of two orthogonal Fourier plane filters that realize the half-order differentiation is presented. Real semiderivative filt ers used in two dimensions and in sequence yield output-image intensit y signals proportional to the first derivatives of the input-object ph ase that appear on a constant background. This nonlinear filtration of spatial frequencies permits the alleviation of the consequences of sq uare-law detection and makes phase changes visible. Phase changes in g radient-index phosphate glass are calculated experimentally. We discus s the accuracy of the proposed method. (C) 1998 Optical Society of Ame rica.