Research On Key Technologies Of Airborne Multi-Beam Array Detection 3D Imaging Lidar

Three-dimensional imaging lidar is an active radar detection system used to accurately and quickly obtain the three-dimensional spatial information of ground and ground targets.The distance information is obtained by measuring the flight time of the optical pulse or modulated optical signal between the radar and the target.The azimuth information in the plane perpendicular to the beam direction is obtained by scanning or multi-point detection,and the three-dimensional image of the target is obtained by post-processing.It has the advantages of high range measurement accuracy,high angle resolution,strong anti electromagnetic interference and clutter ability,and outstanding real-time data processing.It is currently the most potential means for 3D imaging and detection of targets in complex backgrounds.With the development of multi beam laser beam splitting technology,array transceiver technology,array single photon detection technology,and the continuous maturity of laser and detector components,3D imaging lidar technology has gradually evolved from the early single point scanning system to the linear array push scanning system and large-scale array imaging system.The new generation of 3D imaging lidar characterized by multi beam parallel transceiver and array single photon detection is getting faster and faster,with higher detection sensitivity.At the same time,the new system also further reduces the volume,weight and power consumption of the radar system,and effectively improves the reliability and practicality.Based on the theory,system and index analysis of airborne 3D imaging lidar,a 3D imaging lidar system with multi beam high repetition frequency micro pulse laser emission and array single photon detection is simulated and designed in this paper.The principle prototype is developed,and the radar performance is verified in the ground and airborne hang-up flight tests,which can effectively solve the problem of long-distance,high-resolution,high-precision and high-efficiency laser 3D imaging.The innovative work of this paper mainly includes:(1)The optimization design model of airborne multi beam array detection 3D imaging lidar is established,which takes the system index,target characteristics,background characteristics,platform index and other factors as design variables,including spatial geometry model,radiometric model and detection model.On this basis,the detection performance and error influence of the system are analyzed by computer simulation,which provides a theoretical basis for the system design and parameter optimization of multi beam array detection 3D imaging lidar.(2)An innovative implementation method of multi beam array detection 3D imaging lidar system is proposed.The system realizes multi beam laser parallel emission based on diffraction devices,and multi beam laser echo signal array reception based on image telecentric lens,array fiber and single photon array detector.It solves the problems of short operating range and low imaging frame rate of the traditional 3D imaging lidar,and has passed the ground test and airborne flight test of the prototype.(3)A multi beam lidar transmit receive beam matching method is proposed.The error sources in the process of multi beam transmit receive matching and the relationship with the system parameter design are systematically analyzed and simulated.A 64 beam two-dimensional tilted array optical transmit receive system is designed and the transmit receive matching is realized.The high-precision transmit receive matching with 64 beams better than 10 urad is realized.(4)A multi-channel time-of-flight measurement and correction method based on FPGA is proposed and implemented.In this method,64 channel photon time-of-flight measurement is realized by using the internal carry chain of FPGA,and online correction is carried out,which effectively eliminates the deterioration of time measurement accuracy caused by device temperature changes,and the time difference measurement accuracy is better than 100 ps.(5)A 2D profile photon point cloud processing algorithm based on density and local statistics is proposed and implemented to effectively extract target information under ultra-low signal-to-noise ratio.It solves the problems of poor universality and poor target information extraction ability of a single filtering method,and effectively reduces the amount of computation.The airborne flight test verifies that the method has good adaptability to different scenes and different point cloud densities.