Correlation measurements using clipped laser speckle

Clipped laser speckle is used to measure the correlation of time-varying laser speckle. As with standard intensity correlation, clipped speckle is correlated to determine the magnitude of the correlation coefficient. The simple nature of clipped speckle permits high-speed measurements of correlation and velocity. A closed form approximation to the clipped correlation function valid for arbitrary clipping thresholds is presented. The approximation is used to make correlation measurements on speckle from a rotating diffuser using a 2-D random access detector array.