A speckle velocimeter using a semiconductor laser with external optical feedback from a moving surface: effects of system parameters on the reproducibility and accuracy of measurements

Abstract

A speckle velocimeter exploiting the effects of external optical feedback in a semiconductor laser is analysed. The laser diode is used both as the light source and as the detector making the system self-detecting and self-aligning with a single optical axis. The velocimeter employs an autocorrelation method to analyse the detected self-mixing speckle signal. The linear relation between the velocity and the reciprocal of the autocorrelation time of fluctuations in the amplitude of the speckle signal allows the determination of the velocity. Effects of various parameters of the measurement system are analysed and the dependences of the reproducibility and accuracy of the measurements on these parameters are discussed in order to achieve optimization of the system. The optimized system has a measurement error of less than 1.4% within the range of calibration velocities and less than 2.7% outside this range.

Laser feedback interferometry and applications: a review

“…The relative error drops dramatically with the incident angle increasing from 5 to 30 deg. Özdemir et al 77 proposed the autocorrelation data processing method for speckle selfmixing velocimeter; effects of various parameters have been analyzed and the system has been optimized with fewer measurement errors. The linear relation between the reciprocal of the autocorrelation time of the speckle signal obtained and the velocity of the target has been analyzed.…”

50.5L: Late‐News Paper: A Compact, Laser‐based Optical Scrolling Device

“…Both the gain and the frequency of the laser are affected by the feedback, which changes the laser output. This self-mixing effect can be used to measure the velocity or position of objects [3][4][5][6]. Figure 2 shows the operating principle of self-mixing velocimetry.…”