Size determination of mixed liquid and frozen water droplets using interferometric out-of-focus imaging

•Interferometric out-of-focus imaging is used to measure size of liquid and frozen water droplets.•Results are validated using digital in-line holography.•Rate of errors is evaluated.

We record simultaneously interferometric out-of-focus images and digital in-line holograms of liquid and frozen water droplets. We show that the analysis of speckle-like out-of-focus images allows a quantitative estimation of the size of the particles which is corroborated by numerical reconstruction of holograms recorded simultaneously. Interferometric out-of-focus imaging could be extended to the characterization of ice in clouds in the atmosphere.