Development of three configurations of dual-beam interferometric particle imaging for opaque metal droplet size measurement

The micron-sized metallic droplets have been commonly encountered in the utilization of liquid metallic materials. The size of metal droplet is a critical parameter that needs to be determined. This work goes insight into a dual-beam interferometric particle imaging (DIPI) method, which is proposed for the size measurement of opaque micron-sized metallic droplets. Three typical DIPI configurations with signals respectively sampling from the backward scattering, forward scattering, and hybrid-direction scattering regions, are analyzed theoretically, and a generalized model is derived. Proof-of-concept experiments are performed. The DIPI interferograms at the three different scattering regions as well as the digital inline hologram of the same metal droplet are simultaneously recorded. Results demonstrate that the diameters obtained by DIPI of three scattering regions are consistent with each other, and the average deviation values of the three are 1.6%, 2.2%, and 1.7%, comparing to the results of digital inline holography. The DIPI provides an accurate approach for the size measurement of opaque droplets. Besides, it can be carried out over a wide range of angles, breaking the rigorous requirement in the arrangement of apparatus.