Abstract
Deformations undergone by a diffuse object can be determined by speckle interferometry. The object, illuminated in coherent light, is photographed on a high resolution emulsion. Two exposures are made, before and after the object has undergone the deformation. The doubly-exposed photographic plate produces diffraction figures that determine the object deformation. These diffraction effects have been calculated and observed by a number of authors. In this article we calculate the diffraction patterns corresponding to some simple object displacements basing ourselves on the fact that the intensity distribution in a speckle pattern can be assumed to be equivalent to an ensemble of sinusoidal gratings of different frequencies and different orientations.