Research On Signal Denoising And Inversion Method Of Scheimflug Lidar Technology

Atmosphere is the environment on which human beings live,and atmospheric monitoring is an important link to improve the atmospheric environment.Scheimflug atmospheric lidar technology(hereinafter referred to as SLidar technology)is a new type of atmospheric lidar technology which can detect the characteristics of atmospheric aerosols.SLidar technology is based on Scheimflug principle and combines advanced laser technology and image sensor technology,to realize the detection and research of atmospheric echo signal.The atmospheric echo signal detected by SLidar technology is inevitably affected by noise,and the main sources are solar background light noise and image sensor noise.Noise will reduce the signal-to-noise ratio,shorten the measurement distance and increase the inversion error.Therefore,denoising the atmospheric echo signal to improve the signal-to-noise ratio is of great significance to the research and application of SLidar technology.This thesis focuses on two aspects of research work: Scheimflug atmospheric lidar noise reduction technology and atmospheric parameter inversion technology,at the same time,respectively introduces its theoretical basis and specific implementation methods.Firstly,the background and significance of atmospheric lidar technology research are introduced in this thesis.Chapter 2 introduces the principle,characteristics and components of the system in detail.Chapter 3 discusses the different denoising technologies of atmospheric lidar signal,focusing on the principle of wavelet transform,and uses the wavelet threshold denoising method to measure the atmospheric lidar.By means of experimental analysis,parameter optimization and experimental comparative analysis,the decomposition level is 5,the wavelet basis is sym6,and the method of improving rule threshold and threshold function is finally determined and become the most suitable wavelet denoising method for SLidar technology,and the signal-to-noise ratio can be increased by 5-7 times after denoising.In the fourth chapter,the inversion algorithm of extinction coefficient of SLidar technology is introduced,and the key steps of signal processing are clarified.The inversion algorithm mainly uses Klett-Fernald algorithm to retrieve the atmospheric extinction coefficient and the inverted atmospheric extinction coefficient and related parameters are obtained.The experimental results show that the atmospheric average extinction coefficient is highly consistent with the atmospheric particulate matter concentration monitored by monitoring stations.