In-Line Digital Holographic Measurement for Liquid-Liquid Flows

This article deals with a direct application of digital in line holography to liquid droplets dispersed in a continuous liquid phase. The droplet size imposes a regime of intermediate-field diffraction hardly explored to date. Acquired diffraction patterns show that the usual dark disk model is not valid and that good agreement is obtained with a mixed model coupling thin lens with opaque disk. Hologram focusing is nevertheless performed with a dedicated automated method. A literature review has been conducted to identify the sharpest autofocus function for our application. In a second step, in order to measure high retention rates, an inverse problem approach is then applied on all the outliers and missing droplets. This hologram restitution treatment has been applied to experimental results with a comparison to independent measurements.