Velocity measurement by a self-mixing laser diode using speckle correlation

We propose a new self-mixing laser diode (SM-LD) speckle velocimeter based on autocorrelation. SM-LD launches and receives reflected light from a moving surface which has a random reflection profile. The speckle signals obtained from SM-LD are processed using autocorrelation. The linear relation between the velocity and the correlation length of the speckle intensity fluctuations allows the determination of the velocity of the target easily. The range of the investigated velocity is 20 mm/s to 450 mm/s.