高速三维成像激光雷达技术的研究
文献类型：学位论文
| 作者 | 罗远 |
| 学位类别 | 博士 |
| 答辩日期 | 2016 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 陈卫标 |
| 关键词 | 三维成像 激光雷达 非机械扫描 无扫描 高速 混频调制 |
| 其他题名 | Study of High-speed Three-dimensional Imaging Lidar Technology |
| 中文摘要 | 自上世纪九十年代以来，三维成像激光雷达技术迅猛发展，相对于二维图像，三维成像激光雷达在获得目标二维灰度图像的同时，也可以获得目标的三维图像，图像信息更加丰富，能够更加准确地描述目标的特征，因此，在工程测绘、消费电子、工业生产、航天和军事等方面都有广泛的应用。随着无人驾驶技术、无人机蔽障、机器视觉等新兴技术的发展，对三维成像激光雷达的成像速度、体积、重量等要求也越来越高，基于机械扫描式的三维成像激光雷达技术已经逐渐不能满足新兴应用的需求。本文针对高速三维成像激光雷达技术展开研究，使之满足对三维成像速度要求较高场合的应用需求。 本文概述了目前国内外实现三维成像几种主要的技术途径，介绍了各个技术途径的研究现状和技术特点，对三维成像激光雷达的工作原理进行了理论分析。论文首先进行了机械扫描三维成像激光雷达的研究，分析了其应用的局限性，然后，在国内目前现有条件的基础上，提出了两种实现高速三维成像的技术途径：非机械扫描式和无扫描式三维成像激光雷达技术，针对各个技术途径进行了相关的理论和关键技术研究，提出了系统设计方法，搭建了实验系统，并进行了大量实验，取得了一定的实验结果。 首先，论文进行了机械扫描三维成像激光雷达技术的研究，该技术采用高精度电机带动转镜实现光束的扫描，采用直接飞行时间测量法，结合高精度时间差测量电路，实现对目标的扫描和三维测量。论文介绍了该激光雷达系统的设计方案，搭建了激光雷达工程样机。通过实验结果发现，该技术可以较好地对静态目标进行三维成像，成像精度较高，1064.1m处的测量精度为0.24m。但是由于成像范围较大，为获得较高的点云密度，电机的扫描速度较慢，在最高角度分辨率情况下，获取一幅完整的三维图像需要26min，因此，无法满足对成像速度要求高的场合。 为提升三维成像激光雷达的成像速度，本文先提出声光扫描视频三维成像激光雷达技术，以二维声光扫描器件替代机械转镜，实现光束的高速扫描，具有响应速度较快、体积小、重量轻的优点，能够在小角度范围内实现灵活快速的扫描，便于实现对小范围目标的高速三维成像。论文介绍了二维声光扫描器件的工作机理，并详细介绍了声光扫描视频三维成像激光雷达的系统设计方案，搭建了激光雷达的工程样机。通过实验结果可以得出：该系统在分辨率为63×63时，成像速度为25fps，系统的最大成像范围为5°×5°，最大成像分辨率为240×240，在30m处的测距精度为8.9mm，对于建筑物目标，最大作用距离可达850m，最大作用距离处的测距精度为0.39m。 接着，提出无扫描混频调制的ICMOS高速三维成像激光雷达技术，该技术以一定频率差对激光光源和像增强器增益进行方波调制，回波光信号通过像增强器后产生混频光信号，光信号频率为二者调制频率差，采用高速相机对混频光信号进行采样，通过余弦波-方波鉴相法实现对回波信号相位的测量，获得目标距离，实现三维成像。论文中详细推导了该激光雷达的距离反演表达式，分析了影响测量精度的因素，介绍了系统的设计方案，搭建了实验系统，进行了成像实验，分析了实验结果，并提出了进一步提升系统性能的改进方法。通过实验结果可知，该激光雷达目前的性能参数为：三维成像速度为200fps，分辨率为256×256时，激光雷达的成像范围为4°×4°，最大作用距离为9m，最大测距精度为1.1m。若增大激光的发散角和功率，其最大成像分辨率可达1024×1024，最大成像范围可达16°×16°。通过选用性能更好的探测器件可以改善系统的性能。 最后，对以上三种技术进行了分析比较，机械扫描三维成像激光雷达成像范围大、测量精度高，但成像速度慢；非机械扫描式三维成像激光雷达的测量速度有所提升，且测量距离远、测量精度高，但成像范围小，成像速度也需要进一步提升；无扫描三维成像激光雷达具有探测范围大、分辨率高、成像速度快的优点，但激光功率要求较高、测距精度较低、测量距离近。该三种技术各有优缺点，在实际应用中，应根据需求，选用合适的技术方案。 |
| 英文摘要 | Since the 1990s, three-dimensional (3D) imaging lidar technology has developed rapidly. Compared with the two-dimensional imaging, 3D imaging lidar can measure the 3D image of the target, at the same time obtaining its two-dimensional gray image, which makes characterizing the target more accurately. It had been widely used in engineering surveying, consumer electronics, and industrial production, aerospace and military. With the development of unmanned technology, unmanned aerial vehicles obstacle avoidance, machine vision and other emerging technologies, we require that laser radar has better performance, such as faster imaging speeds, smaller, lighter, etc. The traditional 3D imaging lidar which based on mechanical scanning can’t meet the needs of practical applications. In this paper, we studied the technology of high-speed 3D imaging lidar. This paper outlined the current main technical ways to high-speed 3D imaging, and analyzed the research status and technical characteristics of each approach. This paper studied mechanical scanning 3D imaging lidar, analyzed the limitations of its application. On the basis of the existing domestic conditions, the paper put forward two ways to achieve high-speed 3D imaging: non-mechanical scanning way and non-scanning way. This paper did the theory and key technology research for each technology way, proposed the system design methods, set up the experimental system, and obtained some experimental results. Firstly, the paper studied mechanical scanning 3D imaging lidar technology. the technology used high-precision motor to drive rotating mirror, and combined with high-precision time detection circuit, it can achieve scanning and three-dimensional measurement . This paper introduced the design of lidar system. From the experimental results, we found that the technique can get better performance when imaging static target, and can obtain high imaging precision. The ranging precision is 0.24m at 1064.1m distance. However, due to the larger imaging range, in order to obtain a higher point density, the scanning speed of the system is slow. At the case of highest angular resolution, the system need 26 minutes to obtain a complete 3D image. Therefore, it unable to meet the requirements of high speed imaging application. To enhance the imaging speed of 3D imaging lidar, the paper presented a novel 3D video imaging lidar system based on acousto-optic laser scanning, and solves the problems of low imaging speed, large volume, and large quality which exist in the lidar system based on the traditional mechanical scanning method. Two-dimensional acousto-optic scanning device can achieve fast scanning within a small angular range which makes high-speed 3D imaging possible. This paper analyzed the optical characteristics of target reflection and background, and also analyzed the various influence factors on the measured results. The signal-to-noise ratio expression of the lidar system was deduced. This paper introduced the work mechanism of the two-dimensional acousto-optic scanning device, and described the principle of the system, system components, and the experimental results in detail. From the experiment results, we can know that the imaging speed is 25 fps when the image resolution is 63 × 63, the maximum imaging range of the laser radar is 5 ° × 5 °, the maximum imaging resolution is 240 × 240, for the building target, the maximum operation distance is 850m, the ranging precision is 8.9mm at 30m, and 0.39m at the maximum operation distance. Then, this paper proposed non-scanning difference frequency modulation ICMOS high-speed 3D imaging lidar technology. The lidar modulated the laser intensity and image intensifier gain with two kinds of square wave which were of difference frequency. When the optical echo signal received by the image intensifier, it will generate low-frequency optical signal. Then we use high-speed camera to take sample of this low-frequency optical signal. Through the sampling results, we can calculate the distance information of the target, and achieve 3D imaging. This paper deduced the expression of calculating distance, and analyzed the various influence factors on the measured results. In the paper, the principle of the system, system components, and the experimental results are described in detail, and put forward further improvement methods to improve the system performance. From the experiment results, we can know that the imaging speed is 200 fps when the image resolution is 256 × 256, the imaging range of the lidar is 4 ° × 4 °, the maximum operation distance is 9m, the ranging precision is 1.1m at 6m. If increasing the divergence angle and power of the laser, its maximum imaging resolution can reach 1024 × 1024, the maximum imaging range can be up to 16 °× 16 °. Finally, the paper compared the three kinds of technical methods. The mechanical scanning 3D imaging lidar has the advantages of large working distance ,large working angle range and high precision. But the imaging speed is very slow. Non-mechanical scanning 3D imaging lidar has the advantages of large working distance, high precision and higher imaging speed. But influenced by the device's response time and the scanning angle range, therefore, its imaging range are smaller, and its imaging speed is also required further improve. Non-scanning 3D imaging lidar has the advantages of large imaging range, high resolution and high imaging speed, but at the same time, it needs higher laser power. Its ranging precision is also very low. According to the application requirements, we can choose a more suitable technical solution in practical application. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15961]  |
| 专题 | 上海光学精密机械研究所_学位论文 |
| 推荐引用方式 GB/T 7714 | 罗远. 高速三维成像激光雷达技术的研究[D]. 中国科学院上海光学精密机械研究所. 2016. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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