Statistical properties of speckle are presented that are independent of the diffusion model. When the object correlation area is much smaller than the resolution cell of the imaging system, the amplitude statistics of a fully developed speckle pattern are generally noncircular Gaussian and depend on the second-order moments of the object transmittance and on the point-spread function of the imaging system. The intensity contrast always lies between 1 and . For the Goodman model the contrast is unity, and the amplitude is circular Gaussian, but, when the point-spread function satisfies certain conditions, the contrast is found to be unity independently of the object statistics. In particular, it is shown that these conditions are met when the pupil stop is shifted sufficiently off the axis. For the other limiting contrast value, , general conditions on the object are given. An object corresponding to this case has been synthesized with a computed hologram, and experimental values of the contrast are presented. Finally, the autocorrelation function of the image intensity is calculated.
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