Comparison of aspect ratios of ellipsoidal particles through interferometric out-of-focus images

Based on the interferometric particle imaging (IPI) technology, we present a method for comparison of aspect ratios of ellipsoidal particles. By simulating the interference in-focus and out-of-focus images of transparent ellipsoidal particles with different aspect ratios, we find that, under the same orientation angle, the larger the particle aspect ratio is, the higher the spatial frequency of the out-of-focus image. The IPI system is established to experimentally acquire the out-of-focus images of the transparent ellipsoidal particles. Because the experimental results agree with the simulation, we propose a method to compare the aspect ratios of ellipsoidal particles using out-of-focus images. The method features potential applications in particle measurements. (c) 2021 Optical Society of America