Laser Diode Self-Mixing Technique for Optical Metrology Apllications

This paper proposed a technique for the distance or displacement measurement, based on the optical interferometer known as self-mixing interference. The principle of system is the light from the laser diode is launched into a tested sample, then the reflected light is allowed to re-enter the laser cavity and detected by its own photodiode. The result is analyzed by mathematical relationship between the feedback signal from photodiode and the displacement, give the calibration equation. With the advantage of adjustable beam size and non-contact measurement of this technique, it is properly to develop for measurement the deepness hole with small cross-section.

Keywords:  self-mixing interference, optical metrology

Corresponding author: E-mail: cast@kmitl.ac.th