COMPUTATION OF LIGHT-SCATTERING BY AXISYMMETRICAL NONSPHERICAL PARTICLES AND COMPARISON WITH EXPERIMENTAL RESULTS

A laboratory prototype of a novel experimental apparatus for the analy sis of spherical and axisymmetric nonspherical particles in Liquid sus pensions has been developed. This apparatus determines shape, volume, and refractive index, and this is the main difference of this apparatu s from commercially available particle analyzers. Characterization is based on the scattering of a monochromatic laser beam by particles [wh ich can be inorganic, organic, or biological (such as red blood cells and bacteria)] and on the strong relation between the light-scattering pattern and the morphology and the volume, shape, and refractive inde x of the particles. To keep things relatively simple, first me focus a ttention on axisymmetrical particles, in which case hydrodynamic align ment can be used to simplify signal gathering and processing. Fast and reliable characterization is achieved by comparison of certain proper ly selected characteristics of the scattered-light pattern with the co rresponding theoretical values, which are readily derived from theoret ical data and are stored in a look-up table, The data in this table we re generated with a powerful boundary-element method, which can solve the direct scattering problem for virtually arbitrary shapes. A specia lly developed fast pattern-recognition technique makes possible the on -line characterization of axisymmetric particles. Successful results w ith red blood cells and bacteria are presented. (C) 1998 Optical Socie ty of America OCIS codes: 290.0290, 290.5850, 120.5710, 170.1470, 120. 5820, 000.3860.