菲涅耳变换望远镜成像激光雷达体系结构与算法研究
文献类型：学位论文
| 作者 | 吕笑宇 |
| 学位类别 | 博士 |
| 答辩日期 | 2012 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 刘立人 |
| 关键词 | 高分辨率成像，菲涅耳望远术，傅里叶望远术，重采样插值，光束扫描 |
| 其他题名 | The Architecture and Imaging Algorithm of Fresnel Telescope Imaging Ladar |
| 中文摘要 | 实现高分辨率成像，是目标探测和目标识别领域一项重要的工作，其在战略防御和侦察监视等方面具有战略性发展地位。随着激光技术的发展，激光成像系统越来越多的应用于军事和商业领域。合成孔径激光成像雷达、傅里叶望远术、光学扫描全息术等多种高分辨率非传统成像技术得到研究和发展。 菲涅耳变换望远镜成像激光雷达（菲涅耳望远术）是一种全新体制的高分辨率成像技术，原理是对目标投射一个扫描的由两个同轴同心偏振正交的球面波组成的光斑，目标与照明光斑的相互二维扫描将每个目标点的回波转化为时间流信号，接收端采用同轴相干接收，同时将物体点编码成为一个二维菲涅耳波带结构的复数二次项相位分布，最终通过处理器的匹配滤波重构出物体图像。菲涅耳望远术结合了傅里叶望远术和光学扫描全息术的优点，能够实现目标超光学衍射极限分辨率的二维成像。由于实施了空间对时间的传输信号转化并且采用了同轴光束相干探测和复数相位合成，提高了接收灵敏度和成像信噪比，大大降低了大气对于激光传输的影响。 本文从以下几个方面对菲涅耳望远术进行了研究： 1.菲涅耳变换望远镜成像雷激光雷达原理。本文在傅里叶望远术、光学扫描全息术的基础上提出了菲涅耳望远术的原理，给出了其实现的体系结构和算法。菲涅耳望远术能够获得超越光学衍射极限分辨率的图像，对二维信号采用统一的处理方式，更加易于工程实现。本章对菲涅耳望远术的光学发射系统、基本扫描工作模式、信号收集和处理等关键技术进行了阐述。对菲涅耳望远术静止目标成像模式进行了计算机仿真和实验验证，结果与理论预测结果相符，验证了该成像体系和成像算法的可行性。 2.菲涅耳望远术运动目标重采样插值成像算法。在对运动目标成像的应用领域，本文研究了菲涅耳望远术一维扫描工作模式，并且着重对重采样插值成像算法进行了研究。对于运动目标，利用光束扫描器控制光束做一维扫描，目标与扫描光束的相对运动使得空间-时间变换后的采样点呈非均匀分布，影响了图像重建的进行。这里采用重采样插值算法对非均匀采样数据进行处理，并结合不同的点、面目标，对最近邻插值、双线性插值和立方卷积插值等三种方法分别进行了仿真，并结合仿真结果进行数值分析，在此基础上选择立方卷积插值作为菲涅耳望远术的插值方法。仿真结果与理论预测结果相符，验证了运动目标重采样插值算法的正确性和可行性。 3.菲涅耳望远术扫描方式的设计和优化。为了扩展菲涅耳望远术的应用领域，实现高速飞行模式机载成像，结合机载海洋激光雷达的扫描方式，我们研究了能够实现快速扫描的圆锥扫描工作模式。进一步，我们对广泛应用的光机振镜扫描方式进行了分析和优化。针对正弦扫描模式中存在的扫描非均匀性问题，本文对正弦扫描轨迹进行了数值计算，并定义了非均匀度函数对非均匀性进行分析。针对常用的边缘数据去除的非均匀扫描处理方法，进行了计算和仿真，证明该方法的局限性。接着提出更适合于菲涅耳望远术的重采样插值优化方法，并进行了一维点目标和二维点目标的计算机仿真模拟，证明该方式能有效改善光机振镜正弦扫描的均匀性，实现机载模式菲涅耳望远术的高速扫描成像。 |
| 英文摘要 | Obtaining high resolution image is a constant work in object detection and identification, which is very important in early warning, strategic defensive, reconnaissance and surveillance. Various types of non-traditional laser imaging systems are developed to satisfy military and commercial applications, such as synthetic aperture imaging ladar, Fourier telescopy and optical scanning holography. A new high resolution laser imaging system is demonstrated. This system, referred to as Fresnel telescopy (short for Fresnel telescope imaging ladar), uses two coaxial cross-polarized beams to scan objects. Two-dimensional relative motion between target and scanning beams transforms a target point into Fresnel zone plate structure complex quadratic term. We use coherent detection and use matched filtering to reconstruct the target image. Fresnel telescopy combines the advantages of optical scanning holography and Fourier telescopy, which can achieve better imaging resolution than optical diffraction limitation. As we transform reflect signal from spatial domain to time domain and use coaxial coherent detection, the sensitivity is improved and the impact of atmosphere in laser transmission is reduced. In this paper, we do research with Fresnel telescopy in several following parts: 1. We design the basic theory and algorithm of Fresnel telescope imaging ladar. We discuss several important high resolution imaging techniques, especially Fourier telescopy and optical scanning holography. On the base of this work, we propose a new high resolution laser scanning imaging technique, which is so called Fresnel telescopy, and can achieve better imaging resolution than optical diffraction limitation. What’s more, Fresnel telescopy deals with two-dimensional signal with the same imaging algorithm, which is easier to be achieved than synthetic aperture imaging ladar. In this chapter, we introduce the key techniques of Fresnel telescopy, which are optical emission system, basic scanning operational mode, signal collection and processing. We propose the imaging algorithm for static target and do simulation. The results match the theory prediction, which validate the imaging system and imaging algorithm. 2. We propose resampling interpolation imaging algorithm for moving target of Fresnel telescopy. We use one dimensional beam scanning for moving target, and the relative motion between target and beam makes the data be two–dimensional non-uniform distribution, which affects the following matched filtering algorithm. We propose to use resampling interpolation to deal with non-uniform data. We have done computer simulation with three different interpolation methods with point and area targets. Then we do numerical calculation with the interpolation results, and prove that the cubic interpolation is more suitable for Fresnel telescopy. The simulation results match the theory prediction and validate the resampling interpolation algorithm. 3. We design and optimize the scanning modes of airborne Fresnel telescopy. In order to expand the application field of Fresnel telescopy, we analyze palmer scanning operational mode, which can achieve fast scanning. Furthermore, we do research with the widely used scanning galvanometer. As fast scanning mode includes non-uniform sampling problem, we do mathematic calculation with fast sinusoidal scanning track. Then we analyze the usual method which delete the data in both scanning edges, and prove that it is not suitable for Fresnel telescopy. Then we propose to use resampling interpolation to deal with the non-uniform scanning data, and do simulation with one-dimensional point target and two-dimensional point target. The simulation results prove that this method can improve the uniformity of sinusoidal scanning, and achieve high speed scanning in airborne Fresnel telescopy. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15703]  |
| 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 | 吕笑宇. 菲涅耳变换望远镜成像激光雷达体系结构与算法研究[D]. 中国科学院上海光学精密机械研究所. 2012. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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