Real-time moire interferometry

A high frequency moire interferometry technique to continuously monitor in-plane surface displacement is presented. This approach employs fiber optics and a thermoplastic device to holographically record the initial carrier pattern produced on the surface of a test specimen. The carrier is modulated as the specimen deforms and moire fringes, indicative of in-plane displacement, are observed in real time. Unwanted holo-interferometric patterns are eliminated by appropriately adjusting the polarization of the reference wavefront. This paper describes a demonstration of the real-time technique as applied to the study of deformations in a notched beam subjected to a three point loading.