Research On Synthetic Wavelength Displacement Measurement And Signal Processing Based On SelfInterference

Laser self-mixing interferometry has the advantages of high precision,easy collimation,compact structure and non-contact.It can be applied to the measurement of physical quantities such as distance,displacement and velocity in the fields of industry,biomedicine and national defense.Displacement measurement is an important direction in the application of laser self-mixing interferometry,which uses the self-mixing signals generated by vibrating objects to extract the displacement information of objects by analyzing and processing the signals with external vibration,so as to measure the displacement.In order to improve the accuracy of measurement results and reduce measurement errors,this paper,based on self-mixing interference technology,constructs a synthetic wavelength vibration displacement measurement system based on laser self-mixing interference.The specific work is as follows:1.This paper introduces the theoretical basis of laser self-mixing interference,analyzes the traditional three-mirror cavity self-mixing interference theoretical model,and deduces the power equation,phase equation and the relationship between phase and displacement of laser self-mixing interference.2.In order to improve the resolution of the signal,the theoretical model of the synthesized wavelength is analyzed and the relation between the synthesized wavelength and the displacement is deduced by means of laser self-mixing interference.The feasibility of the synthetic wavelength displacement measurement method is verified by simulation analysis and experiments for two kinds of vibration: simple harmonic vibration and random vibration.3.In order to solve the limitation of the measurement range of the synthetic wavelength self-mixing interferometer,a secondary envelope extraction algorithm was proposed,which firstly extracted the secondary envelope of the self-mixing signal,and then reconstructed the synthetic wavelength displacement of the normalized self-mixing signal.Through the simulation and the processing of experimental data,the validity and feasibility of the signal processing method with different feedback intensity are proved.