Simultaneous retrieval of particle size and refractive index by extended interferometric particle imaging technique

A method is presented for simultaneously inferring both the refractive index and the size of a particle with extended interferometric particle imaging technique. The optical system of extended IPI with opposite two-sheet illumination at dual scattering angles is laid out for the experiment. The size of a particle is evaluated by the interference fringe recorded at the scattering angle of 90°, which is from the two reflected lights with two counter-propagating sheet illuminations. And then the refractive index is calculated by the fringe pattern recorded in the side scattering angle region with one of two-sheet illumination when combined with droplet size determined. Experiments on the polystyrene microsphere and water droplet suggest that the method presented herein is promising for many relevant applications, such as fuel combustion and environmental monitoring, in accurately measuring both the particle size and its refractive index.