3D shearography for surface strain analysis

摘要

Abstract: The development of a time-division-multiplexed 3D digital shearography instrument is described. The system provides simultaneous measurement of the in-plane and out-of-plane deformation gradients, allowing full surface strain analysis. The object under investigation is sequentially illuminated from three directions by three fiber coupled high power laser diode sources, and imaged onto a CCD camera through a single shearing interferometer. The pulsing of the sources is synchronized with the camera frame rate. Phase stepping is achieved using laser diode wavelength tuning combined with a path length imbalance in the shearing interferometer. The source pulsing schedule and image acquisition are controlled from a PC. An analysis of the optimum illumination geometry is presented. The performance of the system is evaluated on laboratory test samples. !13