Dynamic statistical properties of laser speckle produced by a moving diffuse object under illumination of a Gaussian beam

The dynamic statistical properties of laser speckle produced in the far-field diffraction region by a diffuse object moving in an arbitrary direction of three-dimensional space under illumination of a Gaussian beam are investigated theoretically and experimentally. It is found that the time-varying speckle intensity detected at the center of the far-field diffraction plane is a stationary random process with respect to time. The dependence of the autocorrelation function of the time-varying speckle-intensity fluctuation on both lateral and longitudinal components of the object velocity is studied in some detail by evaluating numerically the resultant equation of the time-varying speckle-intensity correlation. To confirm the theoretical results, an experiment has been performed. Good agreement between the theoretical and experimental results is obtained for the autocorrelation function of the time-varying speckle-intensity fluctuation that is due to three-dimensional translation of the diffuse object.