Measurement of particle size, number density, and velocity using a laser interferometer

A method for determining particle size, number density, and velocity utilizing a laser interferometer is analyzed. The results show that when the fringe spacing is comparable to a particle diameter, size can be estimated; and when the fringe spacing is much greater than the average particle diameter, number density can be measured. Since the optical arrangment for the interferometer is identical to that for a number of laser velocimeters, the effects of particle size on the velocimeter signal are discussed.