#Y2021 #Laser Self-mixing or back-injection laser interferometry is an interferometric technique in which a part of the light reflected by a vibrating target is reflected into the laser cavity, causing a modulation both in amplitude and in frequency of the emitted optical beam. In this way, the laser becomes sensitive to the distance traveled by the reflected beam thus becoming a distance, speed or vibration sensor.The advantage compared to a traditional measurement system is a lower cost thanks to the absence of collimation optics and external photodiodes. [https://en.wikipedia.org/wiki/Self-mixing_laser_interferometry](https://en.wikipedia.org/wiki/Self-mixing_laser_interferometry)