Application of diffraction tomography theory to determine size and shape of spheroidal particles from light scattering

• An algorithm to determine the geometric structure of spheroidal scatterers is proposed.
• The algorithm is based on optical diffraction tomography theory.
• Projection of the scattering potential is reconstructed from angular resolved scattered field.
• The resolution limit is a quarter of a wavelength in the medium.
• Numerical simulation results demonstrate the algorithm.

Discerning the geometry of spheroidal scatterers of micron order is an important topic in identifying marine microbes. Optical diffraction tomography theory indicates that under the first-order Born approximation for weak scattering, scattering amplitude in the far zone and scattering potential of the scatterer have a Fourier relationship. In this paper, we describe a method based on diffraction tomography theory and determine the size and the shape of spheroidal scatterers by reconstructing the distribution of scattering potential from angular resolved scattered field. As a demonstration of this method, the scattering from spheroidal particles with equal-volume-sphere radii of 0.5429, 1.00, and 2.00 μm and an aspect ratio that varies from 0.4 to 1.5 was modeled by using T-matrix theory and used as test data. Simulation results show that in the case of low contrast, size and shape determination can be achieved with sub-wavelength precision.