Laser Speckles Produced by the Longitudinal Motion of a Diffuse Object under Gaussian Beam Illumination

The dynamic statistical properties of laser speckles produced in the far-field diffraction region by the longitudinal motion of a diffuse object under Gaussian beam illumination are experimentally investigated. A new phenomenon, the statistical stationarity of the time-varying speckle intensity detected at the center of the far-field diffraction plane, was observed, despite the fact that the spatial structure of corresponding speckle patterns, characterized, for example, by the average size, varies greatly in time due to changes in both the illuminated object area and the distance from the object to the receiving plane.