System Optimization And Experimental Study Of Lateral Scattering Image Lidar

Aerosol is an important component of the atmosphere.As one of the important factors for affecting atmospheric radiation and climate change,the accurate measurement of its composition distribution,physical morphology and optical properties has far-reaching research significance.At present,there are many methods to achieve the measurement of aerosol optical parameters.As an important application of atmospheric remote sensing measurement technique,Lidar has become an important means of aerosol optical information measurement due to its advantages in the detection of atmospheric parameters,such as wide dynamic range,high spatial and temporal resolution,high detection accuracy,continuous and uninterrupted observation.Due to the system structure of the biastatic backscatter lidar,the bline zone and transition zone of the geometric overlap factor greatly reduces its ability to detect aerosol optical information near the ground.The lateral scattering image lidar is a new method to detect aerosol optical parameters.It uses the monostatic structure of the transceiver system to solve the effect of geometric overlap factor in the backscattering lidar system.However,the inversion accuracy of aerosol optical parameters is affected by the lateral scattering phase function of aerosol because the receiving system receives the lateral scattering echo signal at a certain lateral scattering Angle.Aiming to optimize the inversion accuracy of the lateral scattering image lidar system,which is built by the Lidar Remote Sensing Research Center of Xi’an University of Technology,this thesis investigates the detection method of lateral scattering phase function of aerosol.A laser horizontal level remote sensing measurement system for real-time measurement of lateral scattering phase function of aerosol in the homogeneous atmosphere is established.The laser horizontal level remote sensing measurement system takes the lateral scattering image of laser beam transmitted horizontally by the image sensor in open atmosphere.The lateral scattering phase function of aerosol can be obtained by inversion of the lateral scattering image pixel with the lateral scattering angle.In this thesis,the calibration of laser horizontal level remote sensing system and the inversion process of lateral scattering phase function of aerosol are described in detail.Considering that the lateral scattering image contains not only the effective scattered signal,but also the background noise,the de-noising preprocessing techniques for the lateral scattering image are studied.The applicability of three algorithms,including P parameter segmentation algorithm based on signal proportion,segmentation algorithm based on green component,image subtraction segmentation algorithm based on green component,are investigated fordifferent experimental environment and noise composition in laser horizontal level remote sensing measurement system.Based on the singleness of lateral scattering image background noise in the lateral scattering image,the segmentation algorithm based on green component a are selected as the denoising pretreatment technique.The results show that the denoising preprocessing technique is effective and optimized.The lateral scattering phase function of aerosol measured by the laser horizontal remote sensing system is substituted into the lateral scattering image lidar system as inversion parameters.A compositedlateral scattering image lidar system based on one optical image receiver system is built.The system realizes the sampling of vertical scattering laser beam and horizontal scattering laser beam within a short time interval(10s),which makes the real-time measurements of the lateral scattering phase function of aerosol on the basis of little influence on the experimental results,overcomes the coarse errors and saves the experimental cost.The laser horizontal remote sensing system and the composited lateral scattering image Lidar system are used to carry out the experimental observations respectively.The results of lateral scattering phase function of aerosol measured in the same time period are compared to analyze the variation of the lateral scattering phase function of aerosol.According to different weather pollution conditions,the aerosol extinction coefficient results are analyzed,and the lateral scattering phase function of aerosol is substituted into different periods to take part in the inversion.The experimental results show that the lateral scattering phase function of aerosol is strongly dependent on space and time,and will affect the detection of aerosol optical parameters in the near ground area by the lateral scattering image lidar system.The results show that the real-time measurement of lateral scattering phase function of aerosol has far-reaching research significance for the system optimization of lateral scattering image lidar.