Small-angle light scattering: instrumental design and application to particle sizing

A small-angle integrated light-scattering (SAILS) instrument was designed w ith the innovative use of a diffusing plate and a charge-coupled device (CG D) camera. In contrast to previous small-angle light-scattering instruments , SAILS has few optical surfaces, allowing the direct recovery of scatterin g data. Although this approach bypasses the need for aberration corrections that are due to lenses, geometric corrections still apply and are describe d in detail. The image on the diffusing plate, when photographed by the CCD camera, yields a digitized two-dimensional array, covering the observed sc attering angles from 10 to 20 deg. The size distribution of the scattering particles can be obtained by a discrete inversion of the experimentally obt ained intensity versus angle-scattering curve. The mean radii obtained from this inversion of SAILS data are compared with nominal sizes given by the manufacturer, and standard errors are computed. The results indicate that S AILS is an ideal instrument for the study of particulates and, because of i ts fast readout time, is suitable for studying aggregation phenomena. Howev er, because of the limited Q range of SAILS it is currently not suited for the direct determination of particle diameters smaller than approximately 3 00 nm. (C) 1999 Optical Society of America.