A new analytical expression for the average speckle contrast is derived for surfaces of random roughness at reflection. Rayleigh and Simpson phase probability density distributions of non-zero phase mean value are assumed for the roughness of the surface. The behavior of a speckle contrast with a roughness root mean square of phase deviation is presented. The effect of the spectral light profile, its spectral width, the density of the scatterers of the rough surface and the average time delay between the interfering beams are taken into consideration.

No abstract

Under conditions differing from those subjected for central limit theorem, the spatial autocorrelation function of speckle pattern resulting from illuminated rough surface is investigated. Its dependence on different illuminating apertures and the average of the roughness heights is presented theoretically and experimentally. The experiments were carried out using a set of circular and square apertures having different sizes. The results indicate that, increasing the size of the illuminating aperture leads to a decrease in the width of the main lobe of the spatial autocorrelation function.