A dual-beam differential-type laser Doppler velocimeter using variable fringe spacing is proposed to measure the number density as well as the velocity of homogeneous monodisperse particles. The main function of the system is to investigate the variation in the visibility of the photodetector signal as a function of the crossing angle of the two beams. A preliminary experimental study was conducted to verify the theory. Good agreement between the theoretical and experimental results was obtained.
© 1984 Optical Society of America
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