Holographic particle velocity measurement in the Fraunhofer plane

Double exposure holograms of a moving particle field having a 1-D velocity distribution are produced. The Fraunhofer plane is observed on reconstruction, and it is shown that for a Gaussian velocity distribution, the fringes which modulate the diffraction pattern have spacings characteristic of the peak velocity. Known and measured peak velocities are compared, and the effect of the velocity distribution width on the fringe contrast is demonstrated.