Author: P. Nerin
Absolute Distance and Velocity Measurements by Self-mixing Inside a Microchip Laser
We report in this paper a theoretical and an experimental study of a sensor which uses a self-mixing interference effect inside a microchip laser. Self-mixing interference inside a laser is a well-established idea to achieve, with technical simplicity, a coherent optical detection on either a diffuse or a specular remote reflector. The principle of this technique has been originally demonstrated with several gas lasers, and later, with a variety of sold state lasers for velocity and absolute distance measurements. We demonstrate that the self-mixing approach with a frequency modulated LiTaO_3-Nd:YAG micro- chip laser permits to measure, with a good accuracy, absolute distance and velocity on a raw surface. We show that the resonant behavior of the microchip detector can be used to perform high sensitive detection of absolute distances (1-20 m +/- 0,1 %) and velocities (0.1 25 m/s +/- 1,5%) of a remote scattering target. Such a sensor can be used in several applications where both distance and velocity measurements are necessary with a good accuracy. We will give some insight to design a sensor with sub-millimeter resolution for high precision operation like mechanical control.