Signal-to-noise ratio and autocorrelation function of the image intensity in coherent systems. Sub-Rayleigh and super-Rayleigh conditions

This paper is devoted to developing a scattering model for coherent imaging systems. It describes the statistical properties of the image intensity due to the distribution of scatterers on a subresolution scale. The roughness of the scatterers' strength, the randomness of the spatial architecture, and the birth-death process of the scattering centers are considered. Two parameters of the image intensity are examined for the characterization of the scattering medium: 1) the signal-to-noise ratio (SNR), which permits the distinguishing of sub-Rayleigh (SNR<1) from super-Rayleigh (SNR>1) conditions and 2) the correlation coefficient. These parameters permit the estimation of the roughness and randomness degrees of the structure. The model is then extended to account for specular effects and applied to sea clutter. A quantitative treatment of the spatial and temporal correlation characteristics, based on a physical understanding of the underlying process, is derived. Experimental results are presented to validate the model.