Study On Simultaneous Measurement Of Multiple Physical Parameters Based On Laser Self-mixing Effect

The measuring technology based on self-mixing effect has simulated great interest in optical field to exploit application area, measure multiple physical parameters and acquire multiple degree information due to its important advantages in simplicity, low cost and non-contact. We have constructed high precision eelf-mixing laser system for measuring vibration and angle simultaneously, measuring velocity and displacement and acquiring two-degree information of moving target based on multiple feedback effect and laser modulation with triangle waveform. The main works are as follows:1. We have analyzed laser characteristics of optical frequency and intensity and laser self-mixing effect in weak optical feedback regime based on three mirror model. The theoretical analysis of laser self-mixing effect with different effective length from 1 to 20 mm and refractivity from 1.526 to 1.933 of laser resonant cavity are carried on by numerical simulation. The results show that it is helpful for enhancing laser self-mixing effect by decreasing length and refractivity of laser resonant cavity.2. The laser self-mixing signal caused by back-scattering light of particles is simulated using random signal theory on condition of different particle size. The power spectral density of the simulated signal is fit by Lorentz formula and the particle size of aerosol from 0.5 to 3 micron with an error less than 11% is inversed from the fitting results.3.The dual optical feedback effect of laser self-mixing interference is described, whose sourced and factors are analyzed by simulation and experiments. The theoretical and experimental results show that the dual optical feedback results from twice reflection of light in the external cavity. The ratio of two reflected lights’ effect intensity and difference of two reflected lights’ effect phases are both important factors.4.The fiber single-channel system for measuring vibration and angle is constructed based on self-mixing effect in DFB laser using dual optical feedback. The experimental results show that the measured angle is from 0.990° to 1.02°with an error less than 12.1% and the measured vibration amplitude is from Oto 3000mVpp with an error less than 1%, and the resolution is 387.5nm.5. The fiber single-channel system for measuring velocity is constructed based on self-mixing effect in DFB laser. The experimental results show that the measured velocity is from 0.016 to 0.47m/s with an error less than 5.3% and the measured displacement is from 1to 23mm with an error less than 9.8%. The effects of triangle waveform’s amplitude, frequency and asymmetry on experimental results are also analyzed for efficient modulation.6.The fiber two-channel system for measuring velocity is constructed based on self-mixing effect in DFB laser. The experimental results show that the measurement errors in two channels are 7.3% and 8.6% respectively. There are two methods of error reduction. The measurement errors using symmetrical or orthogonal incident lights are reduced to 5.2% and 6.8% respectivelyt. The results are both better than one using two channels individually.