Implementation of the reflection phase-shift laser self-mixing interferometer for large-scale displacement measurement

Abstract

Beginning with introducing π/2 phase-shift on the laser self-mixing front output signal reflected by the metal–dielectric film, the new measurement technique of laser self-mixing interferometer is studied. Through the glass substrate coated by metal film attenuating the laser intensity while introducing π/2 phase-shift on the reflection self-mixing interference front signal in the electronic domain, it is easy to make the laser self-mixing interferometer system work under weak feedback conditions and to produce two orthogonal interference signals which are used to measure the displacement. The simulation result indicates high measurement accuracy. In order to improve the measurement accuracy and resolution of interferometer in 100mm level displacement, the collected self-mixing interference signal is dealt with electronics subdivision in the digital domain, improving the noise performance and measurement reliability. Calibration experiments with high precision guide shows that 0.4μm resolution in 100mm displacement measurement process is achieved. As the self-mixing interference signals are acquired directly, the system measurement speed can be high. But subject to sampling rate of the data collection and processing system, the speed can reach close to 100mm/s in 100mm range displacement measurement theoretically.