Design of a two color two spot laser velocimeter

The design of a two color two spot laser velocimeter based on an argon ion laser and using backscattered light is presented. The equations necessary for determining the parameters of the transmitting optics for optimum focusing of the laser beam are developed. A prism assembly that is used for splitting the laser beam into a 514.5 nm beam and a 488.0 nm beam, rotating the 2 beams, and varying the separation of the beams at the target, is shown. The equations used to determine the signal power collected by a bistatic receiver from a particle crossing the beams is presented. Finally, the results from an experimental system are used to verify the theoretical calculations for particles that are 50 and l00 meters from the transmitter.