Multiplicative electronic speckle-pattern interferometry fringes.

A theoretical analysis of fringe patterns and its experimental corroboration obtained by multiplication of two speckled images with electronic speckle-pattern interferometry (ESPI) are reported. A specifically designed digital filter is used to enhance the contrast and visibility of the inherently noisy multiplication fringes. Phase retrieval is achieved by a phase-stepping technique. Experimental results are presented for the in-plane-sensitive optical ESPI setup; however, out-of-plane and shearing setups may be used as well. The method represents an alternative to the subtraction and addition techniques in ESPI.