Development Of Lidar System For Comprehensive Measurement Of Atmospheric Transmittance,Coherence Length And Wind

Atmospheric transmittance,atmospheric turbulence and atmospheric wind field are very important atmospheric parameters,which play a key role in the field of laser atmospheric transmission.The atmospheric transmittance directly measures the energy attenuation of the laser.Atmospheric turbulence affects the phase distribution,light intensity fluctuation,and beam drift of the laser in space.The atmospheric wind field affects the medium distribution in space and has a significant impact on the thermal halo effect in the field of nonlinear optics,thereby further affecting the atmospheric transmittance and atmospheric turbulence characteristics.Therefore,the comprehensive detection of atmospheric transmittance,atmospheric turbulence characteristics and atmospheric wind field is particularly important.Aiming at the needs of atmospheric transmittance,atmospheric turbulence characteristics and wind comprehensive detection,this paper developed a set of atmospheric transmittance,coherence length and wind comprehensive measurement lidar system(AC W-Lidar system for short)through the integrated design of optics and mechanics.The system bridges the gaps in simultaneous,common-path measurements of atmospheric transmittance,atmospheric coherence length,and wind.Through the indepth study of the technology of lidar detecting atmospheric coherent length(r0 for short),the application scope of focusing and collimating schemes is given,and the accuracy of range gating is controlled.It can effectively solve the problem of inconvenient r0 measurement at different altitudes,and can scan the atmospheric wind field.This algorithm ensures the stable and high-precision operation of ACW-Lidar system.The paper firstly proposes the overall development plan of ACW-Lidar system according to the requirement analysis and design index.Then the design indicators are decomposed,and key indicators such as wavelength,detection accuracy,detection height,temporal and spatial resolution,and scanning range are simulated,calculated and analyzed respectively.According to the analysis results,according to the design idea of optical-mechanical integration,the transmitting unit,receiving unit,detection unit,data acquisition unit and scanning platform are designed in detail,and the key parts are simulated and analyzed to solve the technical difficulties of multi-parameter lidar system fusion.This paper focuses on in-depth research on the technology of lidar detection r0.First,the important parameters in the DIM-Lidar detection r0 technology are analyzed to determine the key indicators in the DIM-Lidar.Then,the technology of laser guide star is researched,the requirement of laser guide star for spot as a point target is established,and the different application scopes of collimated emission and converged emission are given.Finally,the research on distance gating technology is carried out,and the overall jitter of delay and gate width is controlled within 5ns,and the detection accuracy is controlled within the range of 0.75m.Finally,the comparative observation and result analysis of atmospheric optical parameters are given.Based on the ACW-Lidar system,the detection heights of atmospheric transmittance,atmospheric coherence length and atmospheric wind field are realized:≥ 6km@1064nm;≥6km@532nm;≥3km@1550nm.Through the precise scanning platform,the normalization algorithm of the edge scanning is proposed,which overcomes the problem that the near-field geometric factor of atmospheric transmittance is difficult to correct in real time,effectively solves the problem of inconvenient measurement of the r0 at different altitudes,and realizes the measurement of the wind field.The ACW-Lidar system and the near-surface meteorological automatic observation system were compared,observed and analyzed.The changes in atmospheric transmittance,radial wind speed,and atmospheric turbulence were consistent and highly correlated,which verifies that the developed ACW-Lidar system is accurate.According to the analysis of the results of the comprehensive scanning,it is found that the three key atmospheric parameters in the field of laser atmospheric transmission are interrelated and affect each other,so the simultaneous and common path measurement of atmospheric transmittance,atmospheric coherence length and wind is of great significance.This provides a theoretical and experimental basis for subsequent long-term observation and accumulation of atmospheric parameters and atmospheric parameter correction.