Abstract

Moire interferometry⁽¹⁾ is a technique for measuring the in-plane displacement of an object under stress. Two coherent beams are incident on the specimen at angles corresponding to the +1 and -1 diffraction orders of the grating etched onto the specimen. One diffraction order of each beam is reflected perpendicular to the surface, and these beams interfere to produce a fringe pattern. Local changes in the spatial frequency of the grating due to strain induce deflections of the two beams in opposite directions. As a result the fringe pattern describes contours of constant displacement in the direction perpendicular to the stripes of the grating. Mapping of strain components requires the differentiation of the displacement field by numerical or optical means⁽²⁾.

© 1988 Optical Society of America