Research On Single-photon Lidar Ranging And Imaging Technology

With the development of active laser illumination,single photon sensitivity detectors,and high-precision timers,single photon ranging lidars with high time resolution have emerged.Due to the improvement of detector sensitivity,single photon ranging lidar can achieve target distance detection under extremely low laser echo energy conditions,and has significant advantages in applications such as long-distance target detection and active detection of dim targets.This article expands the research on single photon ranging lidar in three directions: efficient and high spatial resolution height measurement,target position detection,and target attitude recognition.At present,the detection methods of single photon ranging lidar mainly include point by point scanning detection,divergent illumination detection,and beam splitting illumination detection.The receiving end adopts a single pixel single photon detector,while the transmitting end scans the target point by point,resulting in poor detection timeliness;The receiving end adopts an array single photon detector,and the transmitting end adopts divergent illumination method,which has lower laser utilization compared to beam splitting illumination method.When conducting high spatial resolution detection,the pure solid-state beam splitting illumination method still consumes a significant amount of pulse energy.Exploring new detection methods to achieve spatial resolution detection without significantly increasing laser pulse energy has certain research value;Based on single photon lidar for ranging,obtaining the spatial coordinate position of the target can provide prior information for target tracking.Using scanning to detect targets has poor stability.Therefore,improving on the basis of single photon ranging lidar to achieve non scanning target tracking has research significance;Based on single photon ranging lidar,the relative depth of each point of the target can be measured and the three-dimensional features of the target can be restored.The use of single photon counting 3D imaging technology to obtain more dimensional information(target attitude)has certain research significance for estimating the attitude of dim targets,and there is currently relatively little research on this topic.The main research content and innovation points of this article are as follows:(1)Efficient and high spatial resolution height measurement: A high-resolution photon counting ranging method with rotating scanning added to laser beam splitting has been proposed.We have built an experimental system,where the transmitting end uses optical fibers to split the laser beam and illuminate the target,while the receiving end uses array detectors to receive and process multiple laser echo signal photons.Fix the fiber optic bracket on the electric displacement table and simulate the push scanning process by moving the fiber optic bracket;During the push scanning process,the fiber optic bracket was rotated to simulate the rotation scanning process,and the correctness of the proposed method was verified in the laboratory.And the ranging precision,accuracy,and the relationship between the two and photon counting of the system were explored.On the basis of beam splitting illumination,this method expands the detection area by pushing and scanning.During the pushing and scanning process,the laser beam group after splitting is quickly rotated to increase the density of the detected target point cloud,thereby improving the spatial resolution of target detection;The receiving end adopts a single photon array detector to collect laser echo photons in parallel.This method can simultaneously collect data from a large number of target points in parallel,which effectively improves the timeliness of detection compared to the point by point scanning method;Compared to the method of producing pure solid-state laser beam splitting illumination with the same number and density of sampling points,the required laser power is significantly reduced.(2)Gazing type target position detection method: Establish an experimental system,with the transmitter using divergent illumination,and the receiver introducing signal photons into a single pixel single photon detector through optical fibers.By using fibers of different lengths,there is a significant delay between the arrival times of photons received by different receiving subsystems,and then photons arriving at different times are labeled and distinguished.Multiple distances are measured using a single pixel single photon detector without scanning.Subsequently,based on the prior information of the arrangement position of the fiber optic receiver,the spatial position of the target is obtained through experimental calculations.Traditionally,single pixel detectors can only measure one distance information at a time;Although single photon array detectors with independent pixels can simultaneously measure multiple distance information,they are expensive,difficult to integrate,and have thermal pixel interference.This method utilizes a single pixel detector to achieve the functionality of array detectors,avoiding the aforementioned drawbacks;And can gaze and detect the spatial position of the target without scanning.(3)A target attitude recognition method based on single photon counting 3D imaging: A single photon counting 3D imaging experimental system was built using a single photon array detector.The arrival time of laser echo signal photons was collected using time-dependent single photon counting technology,and the distance information of the target was processed.The depth map of the target was successfully obtained through the 3D imaging algorithm(laser ranging was performed at each pixel).Establish a database composed of target depth maps of multiple poses,compare the correlation between the prior depth maps in the database and the actual depth maps of the target,calculate the correlation coefficient between the two,and select the most correlated pose in the database as the actual pose of the target.And the feasibility of the method for complex target motion was verified.Explored the relationship between the success rate of the method and background noise,as well as the correlation coefficient and photon count between the depth map closest to the actual attitude in the library and the actual attitude depth map of the target.Compared to the method that utilizes the correlation between the photon count of the target’s single point laser echo and the target’s attitude(rotation angle),and obtains the actual attitude of the target through photon count matching,the method used in this article extends the echo photons from a single point to the entire target surface and does not fail due to errors in the single point echo photon information due to noise interference;Meanwhile,this method utilizes more information dimensions and fully utilizes the spatial distribution and distance information of the target,which is beneficial for attitude estimation.