Size determination of aerosol particles using the LDA-visibility technique in the backscatter direction

Based on the laser Doppler anemometry (LDA) technique and Mie scattering theory, the visibility-particle size relationship (visibility curve) is computed for spherical particles of complex index of refraction. The analysis is restricted to the backscatter direction, for incident light that is circularly polarized. It is observed that the shape of the visibility curve is greatly influence by the index of refraction of the particle and the optical parameters of the system. The domains of values of the index of refraction for which the visibility technique is feasible is determined for specific values of the optical parameters. The information about these domains are presented in the form of special maps. Preliminary results establish that the LDA-visibility technique is feasible for particle sizing over a limited range of index of refraction with certain restrictions placed on the optical configuration.