A Study of the Semiconductor Laser 2-Focus Velocimeter

A compact laser velocimeter was newly developed based on the principle of a flight-time measurement. A semiconductor laser with the maximum power of 40 mW and wavelength of 830 nm was utilized as a light source, and photodiodes were used to detect the scattered light from seeding particles. The time-of-flight between 2 focus points was measured by a digital counter and was transferred to a personal computer to calculate the flow velocity. The air flow velocity at a nozzle exit was measured by this semiconductor laser 2-focus velocimeter and was compared with the results measured simultaneously by a Pitot tube. Consequently, it was confirmed that a laser 2-focus velocimeter by means of a semiconductor laser could be a useful and low-cost optical measuring instrument.