FIGURE 4.

Results of using the a/LCI analysis technique to measure size of spheroidal particles by using angular scattering distributions calculated using the T-matrix model as input into the analysis. Angular scattering distributions correspond to a particle with an equal volume radius of 3.75 μm, a background refractive index of 1.36, a target refractive index of 1.42, and a size distribution of 2.5%. The polarization and orientation of the light and particle respectively are (a) S₁₁, α = 90°, β = 90°; (b) S₂₂, α = 90°, β = 90°, (c) S₁₁, α = 0°, β = 60°, and (d) S₂₂, α = 0°, β = 90°, where α and β are Euler angles and S₁₁ and S₂₂ are parallel and perpendicular incident polarizations, respectively. The equatorial and polar manifolds are 1 wavelength (830 nm) thick, with the center corresponding to the equatorial and polar axes of the spheroid at that aspect ratio. These results indicate that the size measurement of a spheroidal particle as determined by the a/LCI analysis technique almost universally falls on either the equatorial or polar manifold; however, there is no method of consistently predicting which it will be.