Compact and versatile self-mixing type semiconductor laser Doppler velocimeters with direction-discrimination circuit

A compact vector-velocimeter is described which uses a self-mixing type laser Doppler velocimeter (SM-LDV). It electrically identifies features of the sawtooth-like Doppler beat signal waveform to determine the direction of target motion within a velocity range of 23 mm/s-23 m/s. The range of velocity measured is 0.2 mm/s-34 m/s. The measured vector velocity of a reciprocally moving target as well as a rotating target agrees well with the theoretical value.<>