COMPARATIVE MEASUREMENT BY SPECKLE INTERFEROMETRY USING HOLOGRAPHICALLY RECONSTRUCTED MASTER OBJECT

In this paper a new comparative speckle interferometric technique is p resented: we call it the difference digital speckle pattern interferom etric (DDSPI) method. The technique uses the two holographically recon structed virtual images of the (unloaded and loaded) master object as references to detect the difference in displacement profiles of two ma croscopically similar but microscopically different object surfaces. T he two images corresponding to the two different states of the master object are recorded holographically on one holographic plate or on a t hermoplastic film. So, the method does not require the real presence o f the master object in the comparison process: the master object does not need to be subjected to repeated stresses, and each test object ca n be compared with the very same two states of the master object, whic h makes the method more precise and faster than conventional technique s. (C) 1997 Society of Photo-Optical Instrumentation Engineers.