A differential light scattering photometer has been developed for rapid size analysis of single particles in flow. A fluid stream carrying individual particles in single file intersects a focused laser beam at the primary focal point of an annular strip of an ellipsoidal reflector situated in a scattering chamber. The light scattered from polar angles θ = 2.5–177.5° at azimuthal angles ϕ = 0 and 180°, spanning a circle of 355°, is reflected onto a circular array of 60 photodiodes. The signal processing electronics and computer storage can accept 32 signals/particle at rates up to 1000 particles/sec. Photometer performance is tested by comparing measured responses from individual spherical particles with angular scattering patterns calculated for the particular detector geometry. These patterns exhibit the required symmetry in the two half scattering planes. Response measurements for eight samples with particle diameters of 1.1, 2.7, 5.0, 7.9, 10.0, 12.5, 15.6, and 19.5 μm are consistent with calculated size-response curves. The composition of a mixture of five components with particle diameters of 1.1, 5.0, 10.0, 15.6, and 19.5 μm is determined from an analysis of light scattering measurements at various forward-scattering angles.
© 1980 Optical Society of America
Original Manuscript: August 27, 1979
Published: May 15, 1980
M. Bartholdi, G. C. Salzman, R. D. Hiebert, and M. Kerker, "Differential light scattering photometer for rapid analysis of single particles in flow," Appl. Opt. 19, 1573-1581 (1980)