ABSTRACT
Measurement of velocity is required in several areas; notable of these are fluid mechanics and aerodynamics. Almost all the optical techniques of velocity measurement require a transparent or nearly transparent fluid, which is seeded with particles. They rely for their operation on the detection of scattered light from these seeded particles. In order to measure the components of the velocity, the same sample volume should present the possibility to sense each component separately. The preferred method to calculate the displacement of the scatterer in between two pulses is to perform cross-correlation between the two images. The cross-correlation has a single peak providing magnitude and direction of the velocity. For measuring velocity of projectiles and to record its time history, and for the study of impact phenomena, the Doppler shifted light is fed to a Michelson interferometer with unequal arm lengths.
