光束扫描系统是激光雷达的重要组成部分, 决定了激光雷达的视场范围。为了增大视场范围同时保持一定的角度分辨率, 车载激光雷达中常采用多个半导体激光器作为光源, 而不同激光器的时间响应存在差异, 使激光雷达的不同测距通道之间产生测距互差。 Risley棱镜是一种常用的光束指向器件, 具有扫描范围大、指向精度高等特点, 在车载激光雷达的光束扫描上具备良好的应用前景。本文建立了Risley棱镜的光束指向角模型与扫描轨迹模型, 在此基础上合理设计了扫描系统的光机结构, 解决了Risley棱镜扫描不均匀的问题, 用单路激光光源实现了大视场的二维扫描, 水平视场角和垂直视场角分别达到360°和30.4°, 当激光器脉冲重频为1 MHz, 扫描频率为5 Hz, 扫描线数为30线时, 水平分辨率为0.05°, 垂直分辨率为1.0°。该系统的技术指标与主流车载激光雷达相当, 且消除了多路激光器之间的互差, 可有效提高激光雷达的整体测距精度。

A beam scanning system is a fundamental component of a light detection and ranging (lidar) system, as it determines the field of view (FOV). To increase the FOV and maintain a specific angular resolution, multiple laser diodes are often used in a mobile lidar. However, the time response of different laser diodes is different, resulting in a mutual ranging difference between different ranging channels of the lidar. Risley prisms are outstanding beam pointing devices that offer good prospects for beam scanning of mobile lidars because of their notable features such as large FOVs and high pointing precision. In this study, the optical and mechanical configurations of a scanning system are designed based on the beam-pointing and scan-pattern models, which can realize two-dimensional scanning over a wide FOV. The horizontal and vertical FOVs of the scanning system are 360° and 30.4°, respectively. When the scanning system operates at a frequency of 5 Hz and scan lines of 30 with a 1-MHz repetition rate laser, the horizontal and vertical resolutions are 0.05° and 1.0°, respectively. These performance indicators are comparable with those of mainstream mobile lidars and can meet the actual requirements of mobile lidars. Most importantly, this scanning system can eliminate ranging differences between different channels, and significantly improve the ranging precision of the lidar.