Study On Polarization Control And Splitter System For Full Polarization Lidar

Polarization lidar is the main remote sensing instrument for obtaining fine distribution of cloud phase states.It can distinguish water clouds from ice clouds,but it cannot classify the distribution of ice crystal particles in ice clouds.The direction and morphology of ice particles in ice clouds have a great influence on the atmospheric radiation transport and the numerical calculation of climate models,but no remote sensing instrument can detect it at present.Full-polarization lidar is an instrument with multi-polarization detection on the basis of polarization lidar,which can obtain the depolarization ratio and Mueller matrix of detected objects,and then realize the high-resolution detection of cloud phase states and ice cloud particles.The realization of full polarization lidar detection not only requires the light source to emit multiple polarization states laser,but also needs to realize the simultaneous detection of echo stokes vectors.In this thesis,the key technologies of the full polarization lidar system hardware are studied.A polarization control system for full polarization lidar is designed.Two 1/4 wave plates and one 1/2 wave plate are combined to achieve arbitrary conversion of polarization state.The theoretical numerical calculation of the control scheme is carried out based on Mueller matrix of optical devices,and the error factors of the system are calculated and analyzed.It is proved that the design of the scheme is reasonable,and the control error is less than 0.17,which can satisfy the application of the full polarization lidar.An amplitude-divided simultaneous detection system for full polarization lidar is designed.In the system,beam splitter,polarization splitter prism,linear polarizer and 1/4 wave plate are used to divided the beam into four channels and simultaneously detected,which greatly improves the timeliness of polarization measurement.At the same time,the divided amplitude detection system can realize the detection of all stokes vectors of the measured beam,and improves the problem that the polarization state detection parameters are less at present.A 1064 nm full polarization detection desktop experimental device was built.The six-point calibration method was used to calibrate the system and obtain the matrix.A 4×4 instrument matrix of the standard device was obtained by combining the polarization control terminal and the calibration system matrix.The experimental results show that the deviation of the instrument matrix parameter of the standard device is less than 0.0995.The multi-polarization test was carried out with the calibrated system,and the stokes rms deviation was 0.1267,which is in good agreement with the literature data,and verifies the reliability of the system.