When coherent light crosses a medium having scattering centers an un-uniformly illuminated image is obtained, currently named speckled image, having a statistical distribution of the intensity over the interference field. The speckled image appears as a result of the interference of the wavelets scattered by the scattering centers, each wavelet having a different phase and amplitude in each location of the interference field. The image changes in time as a consequence of the scattering centers (SC hereafter) complex movement of sedimentation and Brownian motion. This produces fluctuations of the image intensity in each location of the interference field. These fluctuations give the aspect of “boiling speckles”[1, 2].

The speckled image can be observed either in free space and is named objective speckle or on the image plane of a diffuse object illuminated by a coherent source; it is named subjective speckle in [1]. The review paper [2] classifies the two types of speckled images as far field speckle and image speckle. In this work the objective speckle, respectively far field speckle is considered. The speckle parameters like size, contrast, intensity and polarization carry information on the scattering media. Dynamical speckle analysis has become a current method to characterize the dynamic behavior of scattering medium such as flow, sediment and Brownian motion. The motion of the speckle field was analyzed by correlometric methods [3, 4, 5] or by laser speckle contrast analysis [6, 7].