Method and apparatus for sensing in-plane deformation of a surface

摘要

A surface on which there is a regular periodic pattern, often a relief pattern (12), is deformed, and in-plane deformation is sensed by illuminating the deformed pattern with a beam (12) of coherent light so that light is reflected as one zero order beam and a plurality of diffracted beams; two of the beams (16,18) are combined so that they interfere in a manner related to the deformation along the direction of intersection of the surface plane with the plane in which the two interfering beams lie. The magnitude and direction of in-plane deformation in one or more directions, and the magnitude and direction of the maximum in-plane stress or strain, can be determined automatically.