Research On High-Precision Laser Self-mixing Sensor System Based On Phase Modulation

With the rapid development of modern science and technology,many fields have increasingly higher requirements for accurate displacement and vibration measurement.Laser self-mixing interference(SMI)technology is an emerging non-contact precision measurement technology.Its system has the advantages of single optical path structure,easy collimation,high sensitivity and direction identification,etc.,which is favored by researchers.It has become an important means for high precision and wide range of displacement vibration measurement.It is briefly introduced the historical background,concept and characteristics of SMI,and systematically described the theoretical research progress and application progress of SMI.Meanwhile,based on the equivalent model of F-P three-mirror cavity,the mathematical model of SMI is deduced and established.By using MATLAB software,we analyze and summarize the influence of the system model parameters on the laser output characteristics.Then,a vibration measurement system with a semiconductor laser as the light source was built,and PZT was taken as the external target to be measured for experimental research to verify the correctness of the theoretical simulation.Based on the above research contents,we propose a new type of transmission phase modulation method,which effectively combines multiple reflection technology and EOM phase modulation technology.A series of simulations and experiments have proved that the introduction of multiple reflection structures in the EOM phase modulation system further improves the measurement accuracy of the system,and realizes a micro-displacement reconstruction far less than λ/2,thereby broadening the measurement range of the system.In the experiment,for the vibration with an amplitude of 44 nm,the reconstruction error is 2.1nm.In addition,we also proposed a new type of self-mixing interferometer based on the reflective phase modulation(RPM)method to achieve nanometer-scale micro-displacement reconstruction.Broaden harmonic components spectrum of the self-mixing signal is produced by employing a high frequency vibrating reflective mirror as the phase modulation device.The simulation results show that as the number of reflections increases,the reconstruction error will decrease accordingly.A series of experiments under different amplitudes show that the reconstruction error of this method is less than 10 nm.When the amplitude is 229 nm,the minimum measured error is 3 nm,which demonstrates the technical advantages and high performance of this method.