the characterization of two-phase flows, e.g. sprays. It is able to determine, contactless, the size (1µm – 500µm) and velocities (up to 200 m/s) of homogeneous spherical particles, e.g. drops, bubbles, etc [...] individual particles can be determined, in addition to the velocities, within an accuracy of about 1 µm. With this so-called phase-Doppler measurement technique, which by now is indispensable in spray
https://www.iae.uni-rostock.de/en/research/optoelectronics-and-photonic-systems/optical-particle-characterization/