Optimization Simulation Analysis And Experimental Verification Of Hyperspectral Resolution Lidar Fixed-Point Temperature Detection System

Air temperature can characterize the thermal characteristics of a certain area,and it is indispensable in the field of theoretical research or in the application of national defense and economic construction.As an active remote sensing device,lidar has been more and more widely used in atmospheric temperature detection due to its advantages of high spatial and temporal resolution,high detection sensitivity and strong anti-interference ability.High spectral resolution lidar（HSRL）can achieve high spatial and temporal resolution detection of atmospheric temperature in the range from the troposphere to the bottom of the stratosphere,and the use of scanning spectroscopy technology to accurately invert temperature can achieve absolute temperature detection.Based on this method,the thesis conducts research and experiments on the optimization of the HSRL absolute detection system for fixed-point air temperature in meteorology.Based on the physical definition of temperature,the thesis uses the confocal cavity scanning F-P interferometer（CFPI）to scan the side scattering spectrum of the air based on the positive correlation between the Rayleigh scattering spectral line width and the air temperature T^1/2,and realizes the fixed-point air temperature.absolute detection.Because the scattering spectrum signal detected by the experiment is not only affected by the environment such as temperature,humidity and air pressure,but also has a close relationship with the parameters of the experimental system.Therefore,studying the influence of parameters such as experimental system on the temperature detection accuracy plays an important role in the absolute detection of HSRL fixed-point temperature.Firstly,starting from the principle of HSRL fixed-point temperature detection,since the temperature is related to Rayleigh scattering,the Rayleigh scattering spectral line is convolved with the CFPI transmittance function,and the control variable method is used to study the step interval of CFPI by numerical calculation.,FSR,FWHM and incident light divergence angle on the temperature detection accuracy;and according to the relationship between Rayleigh scattering intensity and scattering angle to analyze the effect of scattering angle on temperature detection accuracy.The results show that in order to make the temperature detection error less than 1K in the single-variable state,the step interval of CFPI must be less than 67.9 MHz,the FSR should not be less than 10 GHz,the FWHM should be less than 70 MHz,the divergence angle should be 1.0-1.2°,and the receiving scattering angle should be greater than 138°.Secondly,using the optical design software Zemax to simulate the spectroscopic system and complete the simulation analysis.The simulated CFPI scans the Rayleigh scattering line at a temperature of 298.15 K and a pressure of 0 kPa and the Rayleigh-Brillouin scattering line at a temperature of 298.15 K and a pressure of 101.325 kPa,respectively.The results show that the temperature detection error does not exceed At 1K,the two scattering lines were scanned to obtain consistent system parameters:the step interval of CFPI was less than 67.9 MHz,the FSR was not less than 10 GHz,the FWHM was less than 70 MHz,the divergence angle of incident light was 1.0-1.2°,and the axial displacement of CFPI was no more than 2 mm.Finally,using the existing HSRL system,under the condition that the FSR and FWHM of CFPI are determined,the verification experiment of the parameter optimization of the fixed-point temperature detection system is carried out,and the experimental parameters that meet the temperature detection accuracy under single variable are obtained:due to the dark current and other factors in the experiment,the step interval of CFPI is smaller than that of simulation,which must be less than 20 MHz,that is,at least 6 cycles are superimposed in the later data processing;The received scattering angle is greater than 164°;The axial displacement of CFPI shall not exceed 2 mm.The optimized system parameters are used for temperature detection experiments.When the step interval of CFPI is 10MHz,the received scattering angle is 172°,and the axial displacement is 0,the average error of system temperature detection is 0.08 K,and the root mean square error is 1.15 K.