Several possibilities for the use of elastic light scattering in the backscatter range (scattering angle ϑ<sub><i>s</i></sub>> 140 deg) for determination of size, velocity, and refractive index of spherical particles are investigated. First the phase Doppler technique is considered. Numerical simulations of light scattering with the Lorenz-Mie theory are used to show that the phase Doppler technique is unsuitable for such backscatter configurations, except for special measurement conditions. The time-shift (or pulse-displacement) technique is then considered by use of the Fourier-Lorenz-Mie theory. Simulations show that up to four fractional signals can be obtained by use of the technique in backscatter, corresponding to the scattering order or modes: surface wave (long path), reflection, second-order refraction (inner path), and a mixture of second-order refraction (outer path) and surface wave (short path). Signal characteristics as a function of particle size, refractive index, and particle ellipticity are studied. Suggestions for a practical measurement instrument are put forward.
© 2002 Optical Society of America
(240.6690) Optics at surfaces : Surface waves
(280.1740) Remote sensing and sensors : Combustion diagnostics
(280.3340) Remote sensing and sensors : Laser Doppler velocimetry
(290.1350) Scattering : Backscattering
Nils Damaschke, Holger Nobach, Nikolai Semidetnov, and Cameron Tropea, "Optical Particle Sizing in Backscatter," Appl. Opt. 41, 5713-5727 (2002)