Scanning System Design For Vehicle-Mounted LiDAR Based On MEMS Mirror

With the rapid development of driverless technology,Lidar has become an indispensable part of environment sensing system for the driverless vehicle due to its advantages such as high measurement precision,fast response speed,long detection distance and being unaffected by ground clutter.Micro-Electro-Mechanical System(MEMS)Lidar has become one of the most promising Lidar technologies for the requirements of autonomous vehicles application because of its advantages of light weight,high scanning speed and low cost.In this paper,based on the application scenario of Lidar for self-driving car,a vehicle-mounted Lidar optical scanning system based on MEMS mirror is designed to realize large scanning field of view(FOV).The thesis investigates the existing laser scanning methods and analyzes the main technical indicators of vehicle-mounted lidar.On this basis,the design scheme of MEMS mirror optical scanning system suitable for vehicle-mounted Lidar is proposed.By using offaxis parabolic mirror and wide-angle scanning lens,the scanning field of view is expanded.The scanning characteristics of MEMS micromirror were investigated through the scanning test experiment of MEMS mirror.The optical path of the key components in the scanning system was analyzed.And the feasibility of the design scheme was discussed.The off-axis parabolic(OAP)mirror is the key element to achieve linear scanning in the scanning field of view.And the volume of the scanning system is greatly reduced due to the off-axis structure.The length of the whole scanning system is about 1 Ocm.In the end,the system is simulated and optimized using ZEMAX software.The key parameters which determine the scanning performance of Lidar,such as scanning field of view and spot size,are analyzed.The results show that the designed scanning system extend the scanning field of view to 38.76°×59.81°.In the vertical field of view,the amplification factor is 3.876.In the horizontal direction,it is 3.738.There is a good linear relationship between the scanning Angle and the corresponding MEMS mirror mechanical tilt angle.In addition,the size of the spot at 100m is about 17cm.In the whole scanning field of view,there is no obvious deformation of the spot.And the maximum spot does not exceed 20cm.The minimum scanning resolution is 0.1%.The results of the designed scanning system are basically consistent with the designed target.The thesis provides a design scheme for vehicle-mounted Lidar based on MEMS scanning solution.