ANGULAR INTENSITY CORRELATIONS IN THE DOUBLE PASSAGE OF WAVES THROUGHA RANDOM-PHASE SCREEN

The problem of light scattering in folded-path or double-passage confi gurations is studied theoretically. Assuming as the random medium a de ep phase screen that introduces Gaussian-distributed phase fluctuation s, we study the motion of the speckle as the source is moved. Some att ention is also given to the phenomenon of backscattering enhancement. Our analysis is based on a novel expression for the complex amplitude that has a simple physical interpretation. For simplicity, only the on e-dimensional case is considered, but an extension of the analysis to two-dimensional screens is not difficult. Using the factorization prop erties of the moments of a complex Gaussian process, we are able to de rive analytical expressions for the mean intensity and the intensity c orrelation of the backscattered radiation. We find that, in most cases , the speckle field decorrelates rapidly as one moves the angle of inc idence and shifts toward the direction of specular reflection with a r ate of motion that is different from that of the angle of incidence. W e also find conditions under which, when the angle of incidence is mod ified, the speckle pattern produced in the region of observation track s the backscattering direction.