Research And Implementation Of High-resolution Laser Self-Mixing Sensor System

With the continuous development and improvement of laser technology,laser detection technology using laser as a light source has now become an important technical means in various sensing fields.Among various laser-sensing technologies,the sensing method based on the laser self-mixing interference(SMI)effect has the advantages which of simple structure of optical path,easy collimation,judgment of the direction of the target object,and relatively low requirements on the laser source,which favored by the majority of scientific research.After decades of development,the current theory of laser self-mixing interference effect has tended to be perfect,and the application based on self-mixing phenomenon has widely covered the traditional measurement fields such as vibration measurement,velocity measurement,absolute distance measurement,etc.In recent years,various studies have expanded its applications to emerging fields such as terahertz imaging,biomedical testing,and even security.Starting from the overview and advantages of the laser self-mixing interference effect,this paper systematically reviews the theoretical research progress and corresponding classification applications of the laser self-mixing interference effect.After that,the threemirror cavity theoretical model was used to derive the self-mixing interference effect.Based on the model,the simulation was used to systematically study the effect of external cavity phase change ?0,the feedback intensity factor C and the linewidth expansion factor a change on the system output.At the same time,the mathematical model is set to introduce in detail two methods to realize the reconstruction of the target vibration,namely the fringe counting method and the phase decomposition-packaging algorithm.On the basis of the above content,this paper focuses on the contribution of orthogonal signals in optimizing the anti-interference ability of the system,details the method of generating a pair of orthogonal self-mixing interference signals using electro-optic modulator(EOM),and uses the obtained a pair of orthogonal self-mixing signals realize the reconstruction of the displacement of the target vibrating object.In addition,this paper also proposes a fringe multiplication algorithm that can expand the accuracy of the self-mixing interferometric measurement system in the time domain and further increase its measurement range.The algorithm can achieve increasing of accuracy without complicated operations.At the end of this article,a complete high-precision laser self-mixing interferometric measurement system is built by combining quadrature signals and phase multiplication algorithms.The system can detect vibrations at the micrometer and even nanometer level and has good anti-interference ability.