Improved Fringe Carrier Technique For Unambiguous Determination Of Holographically Recorded Displacements

Abstract

This paper presents an improved technique that eliminates the ambiguity in holographic fringe interpretation. The technique is based upon generating a high density linear phase carrier. Introduction of the carrier results in the formation of a fringe pattern that has monotonically increasing fringe orders. Any deformation of the object under study produces a corresponding perturbation of the carrier pattern. If the carrier dominates, the perturbed pattern continues to have monotonically increasing fringe orders and thus allows the fringe order to be determined at any point without ambiguity. The phase change due to deformation alone is obtained by subtracting the known linear carrier from the modulated fringe pattern. The process of data reduction is so straightforward that skillful human interpretation is no longer required. This simplification of the fringe interpretation process will pave the way for automatic data acquisition in holographic interferometry.