Single and multiple droplet sizing by backscattering glory in the micrometric range

The development of measurement techniques capable to be used when the optical access is limited is critical for a large series of applications ranging from combustion to aeronautics. In this paper it will be shown that backward scattering glory can be used to measure droplet size in the micrometric range using a unique optical access. The goal of this paper is first to present the glory as a measurement technique and to develop a wave optic model capable to predict the diameter of a droplet from its glory pattern. Indeed the novelty of this work consists in the fact that, considering the edge rays as major contributors to the glory pattern generated by a spherical droplet, Young's fringe analogy can be directly used to determine its size. The model is numerically validated for droplet size ranging from 10 μm to 1 mm and it is applied to multiple droplets glory pattern. The simplicity of the wave optics model allows both a more straightforward interpretation of the physical phenomena and a quick implementation into data inversion algorithms.