Speckle velocimeter with a self-mixing laser diode: optimization of measurement system, reproducibility and accuracy of measurements

A self-mixing laser diode speckle velocimeter based on autocorrelation of speckle signals is analyzed in detail. In this velocimeter scheme, a semiconductor laser is used both as the source and the detector enabling a self detecting, self-aligning system with a single optical axis. Effects of different parameters (beam spot size, measurement time, etc) of the measurement system are analyzed and the system was optimized for the best accuracy and reproducibility of the measurements. The optimized system has a measurement error less than 1.5% within the range of calibration velocities and less than 3% out of this range.