Abstract

Theory for the second- and fourth-order moments of scalar amplitude in the far zone is presented for a spaced cascade of two thin diffusers, and speckle decorrelation with respect to wavelength, angle of illumination, and relative motion between diffuser planes is described. Experiments are categorized as to their capability in measuring surface roughness, surface correlation function, spacing, and order of diffusers. In the experiments the source illumination is provided by a tunable dye laser while either a single-diode detector or a CCD array can be used to record the speckle pattern. Data recording and processing are both accomplished with a digital computer. Carefully fabricated diffuser sets of the paraboloidal and conical type are used.¹ Two specific remote sensing experiments are described in detail. In the first experiment we sense the spacing between a strong diffuser and a circular aperture by observing speckle decorrelation as the angle of illumination is varied. In the second experiment we measure remotely the spacing and diffuser properties of a cascade of two strong diffusers.

© 1988 Optical Society of America