Object-motion measurements using pulse-echo acoustical speckle and two-dimensional correlation

A basic theory of acoustical speckle and cross-correlation is described which utilizes the ubiquitous wave characteristics in ultrasonics. A computer-based pulse-echo system has been developed. It is interfaced to a VAX11/780 computer which operates the system and performs the data analysis. Data from three tests using specimens of steel, aluminum and Plexiglas are discussed. On each specimen, a pulse-echo scan of a scattering surface is made over some area which represents reference configuration. After the surface is displaced, a pulse-echo scan is made over the same area. A small region of the displaced configuration is correlated with the reference as a measure of object motion.