Research On Technologies Of Photon Counting Lidar Based On Fiber Optics

Photon-counting Lidar based on single photon detect mechanism is a new and effective active detection method.Compared with traditional linear detection method,the sensitivity of Photon-counting Lidar is 100 to 1000 higher.On condition of fixed optical aperture of receiver system,the detection range and number of laser beams can be significantly promoted and system power consumption can be effectively reduced.Therefore photon-counting Lidar is suitable for airborne and spaceborne Lidar whose power and weight resource is limited and has great application prospect for its technical advantage.Photon-counting Lidar will bring brand new measurement method and idea for earth observation especially topographical survey and draw for sake of its high laser PRF(Pulse Recurrence Frequency)and multi-beam character,which has great potential.Fiber optics based method is one of the multiple ways of realization of Photon-counting Lidar,which has great development potential.On the basis of summariz ing the present situation and developing trends of photon-counting lidar,single-photon detector and detection models of photon-counting Lidar,general design method of the lidar system is studied and key parameters of the system are explicitly demonstrated.The key technologies of the system including laser beam splitting and beam FOV compression,ultra narrow bandpass background noise filering and high precision co-axis of transmitter and receiver are studied and verified experimentally,on condition of which,a fiber optics based multi-beam Photon-counting lidar prototype is realized.Critical performances of the lidar prototype are tested and analyzed.We carried out a fixed wing plane based airborne sweep-mode 3-D mapping experiment on high altitude with the Photon-counting Lidar.Mapping data with high accuracy is successfully achieved and the performance of system is successfully tested.This thesis has such innovative points:(1)This thesis realized 51 laser outputs with space beam splitter and fiber beam splitter adopted using one laser source.With the application of LMA(large mode area fiber)and fiber optical link,51 laser spots of near-infrared 1064 nm wavelength array transmitting and receiving is parallel realized.The transmitter FOV(field of view)for the airborne Lidar system is 100 micro radian using fiber array beam splitter and beam expander combination.And a 20 micro radian transmitter FOV is realized in lab.Meantime,the co-axis error is analyzed and experimental verified to be less than 10 micro radian.(2)We realized multi-channel ultra narrow band high transmission rate fiber-coupled optical filter(mean 3dB pass-band 0.26nm@1064nm,transmission rate at central wavelength higher than 60% and mean transmission rate higher than 70%)using fiber coupled multi-coating thin film technology which significantly reduces background noise count rate while using large aperture optical system.Thanks to that,the data needs to be handling is much lower and we did an airborne sweep-mode 3-D mapping experiment under strong sunshine condition.The airborne experiment establishes the basis of the realization of large diameter photon-counting Lidar in the future.(3)We realized the first fiber optics based linear sweep-mode photon-counting Lidar in China with 51 laser beams whose laser spots could be arranged arbitrarily.The first domestic airborne topography survey using photon-counting Lidar was carried out and 3-D topography data digital surface model(DSM)of land buildings were achieved on fixed wing plane under sunshine condition.Parameters of Lidar are calibrated and elevation data is acquired whose elevation and plane accuracy satisfies 1:1000 scale mapping requirement.Performance,reliability and environmental adaptability of the Lidar are tested and verified systematically.