基于二维MEMS振镜的激光雷达系统的光学设计

Optical design for 2D MEMS-based lidar system

近年来人们对具有安全驾驶、智能控制功能的汽车需求增长,使智能驾驶汽车快速发展起来,激光雷达作为智能驾驶的核心传感器之一得到广泛的关注,其中MEMS激光雷达具有高帧率、高分辨率、体积小、成本低的优点,是国内外车载激光雷达的主要发展趋势之一。光学系统是MEMS激光雷达重要组成部分之一,分为发射光学系统和接收光学系统,本文基于镜面直径5mm的二维MEMS振镜设计了发射光学系统,将25W的半导体激光器准直为弧矢方向发散半角为1mrad,子午方向发散半角为3mrad的光束;设计了大相对孔径为1∶1、焦距为11.01mm的镜头作为接收镜头,并提出采用放大倍率为2.2的纤维光锥与16线APD阵列探测器耦合,扩大接收光学系统的视场;APD阵列探测器采用选通模式,提高雷达系统的信噪比。基于此设计结果搭建激光雷达样机,实验验证系统探测距离可达45m,全视场角40°×10°。结果表明系统可一定程度上提高激光雷达探测距离和视场角。

In recent years,people’s demands for automobile safety and intelligence have led to the rapid development of intelligent driving cars.Lidar has attracted widespread attention as an core sensor for intelligent driving cars.Among them,the lidar based on two micro MEMS scanning mirror is an important trend in the development because of its advantages of long distance,high frame rate,high resolution,and the miniaturization and cost reduction.The optical system is an important part of the MEMS lidar,which is divided into a transmitting optical system and a receiving optical system.A 25 W semiconductor laser was collimated to a sagittal divergence angle of 1 mrad and a meridional divergence angle of 2.97 mrad;A large relative aperture 1∶1,short focus(11.01 mm)lens is designed as the receiving lens,and a fiber light cone with a magnification of 2.2 is used to couple with a 16-line APD array detector to expand the field of view of the receiving optical system.Based on this design result,a lidar prototype was built.The APD array detector uses a gating mode to improve the signal-to-noise ratio of the lidar system.Experiments have verified that the lidar system can detect a distance of 45 m and a full field of view of 40°×10°.The results show that the optical system can improve the detection range and angle of view of the lidar.