Laser speckle velocimetry: using modulated dynamic speckle to measure the velocity of moving diffusers.

A new method of measuring the velocity of a moving diffuser (or scattering particles) is proposed. The principle of this type of velocimetry is based on modulating the temporal correlation function of the dynamic speckle using a stationary phase grating in the region of the moving diffuser. This method has been experimentally investigated from measurements of a simple velocity distribution on a uniformly rotating ground glass disk by using a photon-correlation technique. The experimental results show that this modulation type speckle velocimetry is quite precise and sensitive.