Contrast variations in white-light speckle interferometry with application to 3D profilometry

We investigated the interference of a white-light speckle pattern, obtained by reflection from a rough surface, with a reference beam. A theoretical analysis has been developed to derive the expression of the speckle contrast, observed in the image plane of a telescopic system, as a function of all the parameters of the interference device. A numerical evaluation of the contrast dependence on the optical path difference is presented, as well as its experimental verification. On the basis of these results on the speckle contrast properties a method has been developed for 3D profilometry of relatively large optically rough objects, using real-time digital image processing.