DIFFERENTIAL DOPPLER VELOCITY MEASUREMENTS

Observed signal characteristics and measurement accuracy are described for a recently developed noncontacting optical velocity sensing method as applied to extended moving surfaces. This method is based on an optical heterodyne measurement of the difference between two Doppler shifts which are produced in the light scattered through two different angles by the moving surface. It provides convenient measurements of velocity components tangent to extended surfaces that are optically rough. Absolute accuracies to at least 0.1%, and relative accuracies to 0.04% are reported.