Moiré gauging using optical interference patterns

This paper describes a moiré technique for gauging surface deformations of an object or differences in the surface configuration of two similar objects. A grid pattern is generated on the object by illuminating it with a laser interference pattern, and a master negative is made by photographing the illuminated object with a view camera. With the negative occupying its original position, the moiré pattern corresponding to changes in the object can be observed in real time by viewing the image of the deformed or second object through the negative. The technique is noncontacting and quantitative. It is useful with objects of any size, and its sensitivity can be easily adjusted to suit the application.