Particle sizing using laser interferometry

The theory and conditions are summarized under which single spherical particles in the size range of a few micrometers and larger may be sized using the observed fringe visibility in a cross-beam laser velocimeter. Scalar diffraction theory and experimental data are presented to show how the size information in the forward- scattered light is dependent on the collection optics geometry, including the size and shape of source beam stops, which have been neglected in previous analyses. Experimental data are also presented to show that backscattered light may not be usable for this method of sizing in the range of sizes examined.