OPTICAL DIFFRACTION VELOCIMETER

摘要

A laser velocimeter for measuring the relative speed of a surface and a source of coherent light directed at the said surface comprising optical and electrical means for generating two electrical signals one of which corresponds to the content of the speckle pattern produced by illumination of the surface by the light circuit means for obtaining a difference signal from the two electrical signals and frequency measuring means for determining the centre frequency of the signal spectrum of the difference signal to generate an electrical signal indicative of the relative velocity of the surface and source. The device can measure length or distance moved by integrating the velocity signal. The optical and electrical means include a grating in the path to one of two detectors or a linear array of photodetectors alternate ones of which are summed, to provide the two electrical signals one of which corresponds to the speckle pattern.