Research On The Angle Measurement Method Based On Laser Self-mixing Interference

With the rapid development of precision manufacturing technology,highprecision,low-cost and convenient angle measurement has become a new research hotspot.According to the requirements of modern high-precision measurement,the principle and standard of laser self-mixing interference are studied,and the angle measurement method based on laser self-mixing is proposed.Compared with the existing angle measurement methods,the laser self-mixing interference effect proposed in this paper has the advantages of compact structure,simple operation and low cost.It is an important means to achieve high-precision and high-resolution angle measurement method,which is suitable for accurate measurement in non-contact environment.The main research work is as follows:(1)In order to solve the problems of complicated structure and limited measurement range of the existing angle measurement system,and to achieve highprecision angle measurement,a mathematical model of laser self-mixing interference angle measurement is established.It is proposed to measure the angle by combining the laser self-mixing interference technology with the geometric relationship calculation.The simulation experiment of the model is carried out by Matlab software,which verifies the correctness of the mathematical model,and analyzes the influence of the linewidth broadening factor and the optical feedback level factor on the self-mixing interference fringes.(2)The method proposed in this thesis uses the laser as the self-mixing interference light source to measure the optical path difference variation of two parallel beams in the interference light path,calculates the angle value through the geometric relationship,and realizes the high-precision angle measurement.Therefore,according to the principle of beam facula position calibration,a facula position detection device is designed.The device can detect the facula position within the range of micrometer and reduce the influence of laser parallelism on the angle measurement results.(3)In this paper,an angle measuring device based on laser self-mixing interference is built.Firstly,in order to improve the accuracy of the counting method of interference fringes,the noise of self-mixing interference fringes is analyzed,and a hybrid filter is designed to eliminate the noise of the collected signal.Secondly,according to the theory of signal optimization processing,the factors that affect the signal of laser self-mixing interference are analyzed,and the influence of modulation current and reflector velocity on interference signal in actual measurement is also analyzed.Finally,in order to ensure the accuracy and stability of the measurement device,the repeatability experiment proves that the measurement results meet the actual requirements.The experimental results show that the high-precision angle measurement device based on laser self-mixing interference designed in this thesis has the advantages of high accuracy,simple structure and convenient operation,which can meet the needs of high-precision angle measurement.