MULTIPLE-SCATTERING SUPPRESSION BY CROSS-CORRELATION

We describe a new method for characterizing particles in turbid media by cross correlating the scattered intensity fluctuations at two nearb y points in the far field. The cross-correlation function selectively emphasizes single scattering over multiple scattering. The usual dynam ic light-scattering capability of inferring particle size from decay r ate is thus extended to samples that are so turbid as to be visually o paque. The method relies on single-scattering speckle being physically larger than multiple-scattering speckle. With a suitable optical geom etry to select nearby points in the far field or equivalently slightly different scattering wave vectors (of the same magnitude), the multip le-scattering contribution to the cross-correlation function may be re duced and in some cases rendered insignificant. Experimental results d emonstrating the feasibility of this approach are presented. (C) 1997 Optical Society of America.