Displacement-Fields (U,W) Obtained Simultaneously By Moiré Interferometry

A high-frequency phase grating on a specimen surface is illuminated symmetrically by two oblique beams. The diffracted beams emerge with wave front warpages that define both the in-plane U and out-of-plane W displacement fields. Contour maps of these wave fronts, with added carrier fringes, are obtained as a single photographic record. They are manipulated by moiré and optical filtering steps to yield whole-field fringe patterns of U and W. Sensitivities of 0.833 _m/fringe (32.8 _in./fringe) for in-plane displacements and 0.132 _m/fringe (5.2 _m./fringe) for out-of-plane displacements were demonstrated. Since data acquisition is experimentally simple, dynamic as well as static analyses are applicable.