| Temperature and wind field are important parameters of the atmosphere,which are of great significance for studying the laws of atmospheric activity and the safe operation of aircraft.Due to the lack of detection technology,the temperature and wind field observation data in the middle top and bottom regions of the thermosphere(75-115km)of the atmosphere are insufficient.Iron Resonance fluorescence lidar is an important means of detecting this region,with the advantages of high spatial and temporal resolution and high accuracy.However,due to the presence of strong sky background noise during the day,the iron atom signal is submerged,and it is impossible to detect the temperature and wind field in the middle and upper atmosphere.In order to solve the above problems,this paper developed a tunable narrowband filter and applied it to the Iron Resonance fluorescence Doppler lidar developed by our research group,so as to achieve daytime temperature and wind field detection in the upper and lower regions of the atmospheric mesosphere.Based on the investigation of narrowband filtering techniques in lidar detection both at home and abroad,a filtering method is proposed by connecting two air gap Fabry Perot etalons in series and combining them with interference filters.By defining a filter performance evaluation function,a quantitative analysis of the filter performance was conducted,and the bandwidth of the interference filter was determined to be 0.15 nm(center wavelength 372.1 nm);The etalon with low resolution has a bandwidth of 7.4 pm and a free spectral range of 94 pm;The high-resolution etalon has a bandwidth of 2.7 pm and a free spectral range of 30 pm.The packaging structure of the filter was designed and analyzed by finite element method to meet the vehicle transportation conditions;Completed the system design of filter air pressure scanning and control,and achieved precise control of air pressure through PID algorithm.The maximum fluctuation value of air pressure within 12 hours is 0.1 kPa;A desktop experimental platform was built to test that the bandwidth and free spectral range of the F-P etalon meet the design requirements;A tunable narrow band filter is applied to the Iron Resonance fluorescence lidar to obtain daytime Iron Resonance fluorescence detection echo signals and compare the changes in background noise;The bandwidth of the high-resolution etalon in practical applications was determined to be 15.3GHz and the peak transmittance to be 0.34 through pneumatic scanning,and the reasons for the bandwidth broadening were analyzed. |
