Abstract

A technique is described which will provide both magnitude and direction of the transverse component of velocity of a remote target. A laser beam is transmitted toward a remote diffuse target, and the backscattered light is collected and mixed with a suitable local oscillator reference field. The method is based on the general spatiotemporal correlation function of the signal currents from two heterodyne detectors. The time derivative of this function, evaluated at zero time delay, is directly proportional to the component of target velocity parallel to the separation of the detector elements. A two-element by two-element detector array can therefore be used to measure the two orthogonal transverse velocity components. Each component is found from the correlation properties of the signals from diagonally opposed pairs of detector elements. Since the radial velocity component can be found from conventional laser Doppler techniques, all three components of the velocity vector can be measured simultaneously. Practical considerations and experimental results are discussed.

© 1982 Optical Society of America

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