Abstract

We describe the speckle pattern caused by a thick diffuser including a study of decorrelation effects with angle of illumination and wavelength. In the theoretical analysis, the thick diffuser is modeled as a cascade of two idealized thin diffusers separated by a distance z₀. We first consider the general case of speckle from an arbitrary optical system at the output of the diffuser and then specialize to the important case of far-zone speckle. For an idealized thin diffuser, i.e., modeled by a transmission function t (x,y), the far-zone pattern moves as a whole and is centered along the axis of the illumination. However, for the thick diffuser, the detail of the speckle pattern also begins to decorrelate as the shift in angle Δθ increases. We show that in the far-zone case there is a simple relationship between the separation z₀ and the shift Δθ required for decorrelation of the speckle pattern.

© 1986 Optical Society of America