Mie analysis of geometries for phase angle particle sizing interferometry

The phase of the Doppler signal component obtained with a laser Doppler velocimeter was examined analytically for particle sizing applications. The analysis used a complete Lorentz-Mie scattering code capable of predicting the light scattered by spheres, of arbitrary index of refraction, into any designated solid angle located at any designated position relative to the particle coordinates and the Poynting vectors of the multiple input beams. The purpose of this project is to provide extensive, full Mie predictions of the phase-size relation, using laser Doppler velocimeter phase measurements, particularly for the 0.3 to 6 μm size range. Phase information was compared to several other in-situ laser particle sizing interferometer measurements to identify its comparative advantages and disadvantages. Because phase is a function of optical geometry including fringe spacing, collector location, and collector focal length, and of particle index of refraction, as well as particle size, Mie scattering predictions were computed for numerous optical geometries and particle indices of refraction. The approach taken was to use the UTSI devel oped Mie Code, incorporating Pendleton's solution and Son's algorithms to provide extensive predictions of the variations of the LV signal characteristics. This allowed identification of promising optical set ups for optimizing in-situ particle sizing for the 0.3 to 6.2 micron diameter range with index of refraction variations of 1.1 to 3.5.