Modified in-plane electronic speckle pattern shearing interferometry (ESPSI)

Abstract

Two optical methods for obtaining the partial derivatives of in-plane and out-of-plane displacement fields in the in-plane ESPSI configuration using temporal phase stepping for automatic analysis of fringe patterns are described. In the first method lateral shear interferograms of object image fields generated by individual symmetrical illuminating beams are recorded independently. The phases are calculated and their subtraction/addition gives required in-plane/out-of-plane displacement derivatives, respectively. Phase stepping is readily performed in the setup based on fiber optics and modulated laser diode illumination. In the second method two primary interferograms: a conventional in-plane displacement ESPI recording and one with object images mutually laterally displaced are recorded. Similarly, software subtraction or addition is performed to separate the out-of-plane displacement derivatives and double sensitivity in-plane displacement information.