Calibrationl And Experimental Observation Of Full Polarization Lidar Instrument Matrix

Cloud phase detection with lidar has become a popular study issue in the field of atmospheric science detection in recent years.In classic lidar,depolarization was utilized to precisely measure cloud phase,and the depolarization ratio was employed to respond to the non-spherical degree of particles in order to determine cloud phase or dust particle information.However,because directed ice crystals occur in actual air,the polarization ratio is insufficient to reveal the scatterer’s characteristics.As a result,a fully polarized lidar is presented for obtaining the particle backscattering Mueller matrix by amplifying the polarization information,allowing for high accuracy cloud phase identification.The thesis presents a Mueller Matrix Theory-based cloud phase and ice cloud detection method,as well as a totally polarized lidar device.It proposes a polarization control system that includes a polarization splitting prism,a half wave sheet,a quarter wave sheet,and a high precision rotary table to solve the difficulties of high precision control of the polarization state at the laser transmitting end.A Cassegrain telescope and an orthogonal reflector structure are utilized at the laser receiving end for polarization-preserving reception of the echo signal.In order to extract the full Stokes vector in real time,the thesis offers a split-amplitude spectroscopic detection approach that uses common components to detect the entire Stokes vector in real time.The thesis performs laboratory calibration of the spectroscopic system and external calibration of the entire system to solve the problem of a complex fully polarized LIDAR system with numerous optical components and prone to non-polarization characteristics.The entire division-of-amplitude spectroscopic detection system is calibrated using the multi-point calibration method in this thesis.The calibrated instrument matrix was evaluated using 1/4 wave slice after calibration,and the average error between the instrument matrix of the standard device and the theoretical value was 0.13,meeting the experimental requirements.After developing the thin warm cloud echo signal in the atmosphere as a standard source,the full-polarization lidar system’s matrix was calibrated,and the lidar’s instrument calibration matrix was generated using the calibrated results.The total polarization lidar system’s matrix was calibrated after using the thin warm cloud echo signal in the atmosphere as a reference source,and the lidar’s instrument calibration matrix was constructed using the calibrated results.The corrected totally polarized LIDAR system was used in an outfield experiment to identify low-altitude water clouds and high-altitude cirrus clouds,and backscattered Mueller matrix profiles of water clouds and cirrus clouds were calculated.By combining the entire polarization detection theory with the experimental results,a 200m layer of orientated ice crystal band is successfully recognized in the cirrus signal,demonstrating that the experimentally developed system can identify cloud phase state and ice cloud particles.