Sizing homogeneous spherical particles from intensity-only angular scatter.

A set of algorithms is proposed to retrieve the size of spherically symmetric particles from the measured intensity of angular scatter data. Of special interest are low-contrast particles whose real part of the index of refraction is between 1.03 and 1.09 and whose size ka is constrained so that pi < or = ka < or = 16pi, where k=2pi/lambda and a is particle radius. Several algorithms are evaluated and compared that are based on either simple matching to the Mie theory predictions or inverse tomography methods. In the tomography methods, a previously proposed algorithm [Opt. Express. 15, 12217 (2007)] was used after estimating the phase of the scattered data or adapted to use intensity-only data. In order to ensure stability, all algorithms' performance was evaluated in the presence of moderate noise. The performance varied as a function of particle size, refractive index, and algorithm. Results suggest that a scattering device that collects only the angular scatter that is perpendicular to the polarization of incident light, usually denoted as S(1), can be used to accurately estimate the size of homogeneous, low-contrast, spherical particles whose diameters are close to the wavelength of the incident light.