Speckle interferometry with temporal phase evaluation for measuring large-object deformation

We propose a new method for measuring large-object deformations by using temporal evolution of the speckles in speckle interferometry. The principle of the method is that by deforming the object continuously, one obtains fluctuations in the intensity of the speckle. A large number of frames of the object motion are collected to be analyzed later. The phase data for whole-object deformation are then retrieved by inverse Fourier transformation of a filtered spectrum obtained by Fourier transformation of the signal. With this method one is capable of measuring deformations of more than 100 mu m, which is not possible using conventional electronic speckle pattern interferometry. We discuss the underlying principle of the method and the results of the experiments. Some nondestructive testing results are also presented. (C) 1998 Optical Society of America.