Research On The Measurement Method Of Comprehensive Parameters Based On Laser Self-Mixing Interference

With the continuous progress of science and technology,the laser self-mixing interference technology has developed into a relatively mature measurement technology.The laser self mixing interference technology uses the characteristics of the semiconductor laser to measure and experiment.The measurement system composed of the semiconductor laser is not only simple and easy to collimate,but also has the advantages of high precision,precisely because of its high precision,So it is widely used in various fields.This thesis focuses on the measurement of laser self-mixing interference parameters,which are(optical feedback level factor),(linewidth broadening factor)and displacement.For the calculation of and,the symmetrical folding algorithm is given,and the calculation of displacement gives a method to recover the displacement of the outer cavity based on the phase expansion principle,because the accuracy of and directly affects the accuracy of displacement.The main contents of this thesis are as follows:First of all,according to the general theoretical model of self-mixing interference effect derived from the three mirror cavity model method,the numerical simulation of self-mixing interference signal under different feedback levels is carried out,the influence of the parameters in the model and equal parameters on the interference signal is analyzed,the correctness of the theoretical model is verified,the overall framework of the whole system is given and the measurement of the parameters of the laser selfmixing interference is built System.Secondly,most of the signals will contain many sudden changes or sharp peaks.The noise contained in the signals is not all stationary white noise,which will affect the feature points in the signal waveform,thus affecting the calculation of the sum,and ultimately leading to a large displacement error.Aiming at the noise in the signal,this thesis presents an algorithm based on(Ensemble Empirical Mode Decomposition),which is a new de-noising method developed on the basis of(Empirical Mode Decomposition),using this algorithm can effectively remove the noise in the signal,and complete the simulation verification in different degree of optical feedback,which proves the effectiveness of the method.Thirdly,based on the research of de-noising signal,this thesis gives a method to recover the displacement of external cavity based on the principle of phase unwrapping.This method needs to know and.In this thesis,symmetrical folding algorithm is used to find and.On the basis of theory,simulation is used to analyze,which proves the effectiveness of the method and gives the accurate scope of application.Finally,in view of the above simulation verification,experimental verification is made.Through the built measurement system,a large number of repetitive experiments are carried out,data collection and processing are carried out,and the measurement of comprehensive parameters is completed.After verification,simulation analysis and experimental verification are consistent,and the effectiveness of the above methods is verified again,and finally the reasons for possible errors and the methods to reduce errors are given.