Laser speckle velocimeter using self-mixing laser diode

We propose a laser speckle velocimeter using a self-mixing laser diode (SM-LD). It was confirmed that the speckle signal obtained by the measurement system has its waveform independent of the target velocity as far as the same path on the target surface is measured and that the mean frequency of the speckle signal is directly proportional to the target velocity. This mean speckle signal frequency is automatically measured by using a computer and its measurement accuracy against a measuring time was also confirmed by this system. So it will be possible to detect velocity of the target transversely translating against the laser light beam using this compact measuring system