Frequency Domain Analysis Method And Application Research With Laser Self-mixing Interference

In recent years,the Laser self-mixing interference technology using semiconductor lasers has been widely concerned by researchers.Compared with traditional optical interference,it has the advantages of single-arm optical path,easy alignment,and independent of the type of laser.Therefore,it has a comprehensive range of applications in precision measurement,scientific research,defense security and biomedical sensing.Based on the SMI effect of semiconductor lasers,the thesis explores the application of SMI technology in high-precision vibration measurement and material property analysis.Firstly,the research background and significance of laser self-mixing interference are introduced,and the progress in theoretical research and its application in measurement are reviewed.Based on the F-P model,the basic formula of Laser self-mixing interference is deduced and given,and the variation rule of the signal waveform of self-mixing interference under different system parameters is analyzed by MATLAB software.Based on theoretical research and simulation analysis,a semiconductor laser self-mixing interferometric vibration measurement system was built.The PZT and loudspeaker are used as the target to be tested respectively,and compared with the simulation results.For nanometer vibration measurement applications,the thesis proposes a frequency domain signal analysis method based on laser self-mixing interference.The vibration with four different amplitudes are measured experimentally.For the vibration with an amplitude of 35 nm,the measurement error is 0.85 nm.Then,the influence of the amplitude,the reflection times and temperature on the error of measurement results are analyzed.And the method is compared with three existing high-precision vibration measurement methods.Based on this,the frequency domain signal analysis method is applied to the measurement of vibration characteristics of damping materials,and the damping coefficient is calculated by finding the jumping point of the main frequency in the self-mixing frequency domain signal.In the experiment,the tuning fork with a resonance frequency of 128 Hz was used as the target to be tested.The 8 sets of main frequency jump points are fitted linearly,and the fitting degree reached 0.9975,which shows the feasibility of the method in the application of damping measurement.The frequency domain signal analysis method proposed in the thesis verifies the practicability of laser self-mixing interference technology in measuring nano-scale vibration and damping vibration.This deepens the understanding of the effect of laser self-mixing interference effect,and enriches its application in practical measurement to a certain extent.