Velocity measurement using laser speckle statistics

A technique is presented which uses a laser beam to measure both vector components of the transverse velocity of a diffuse target. It is shown that the derivative of the spatio-temporal cross-correlation function of laser speckle intensity fluctuations, taken with respect to the time delay and evaluated at zero time delay, is directly proportional to the component of target velocity that is parallel to the spatial separation. Experimental results are presented which verify this linearity.