Evaluation of measurements of particle size and sample area from optical array probes

Abstract

Presents the theory of spherical particle shadows, using the theory of Fresnel diffraction for an opaque disc. An experimental study of the diffraction images of glass beads suggests that the shadow image size of spherical particles is essentially dependent on the distance from the object plane (possible large errors for smaller particles) . Results agree with calibrations using monodisperse water droplets. Shows that the sample area has a complicated sawtooth shape. Gaps oriented perpendicular to the axis of a laser beam occur in the sample area of large droplets for an optical array probe. (from authors' abstract)