Simultaneous measurement of three displacement derivatives using a multiple image-shearing interferometric camera

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Abstract
This paper describes a multiple image-shearing camera. By incorporating coherent light illumination, the camera serves as a multiple-shearing speckle interferometer which measures the derivatives of surface displacements with respect to three directions simultaneously. The application of the camera to the study of flexural strains in bent plates is shown, and the determination of the complete state of two-dimensional strains is also considered. The multiple image-shearing camera uses an interference phenomenon, but is less demanding than holographic interferometry with respect to vibration isolation and the coherence of the light source. It is superior to other speckle techniques in that the obtained fringes are of much better quality.