QQ客服 官方微博 反馈留言

题名	合成孔径激光成像雷达图像重构及后处理技术研究
作者	李光远
文献子类	博士
导师	孙建锋 研究员
关键词	合成孔径激光成像雷达 Synthetic aperture laser imaging ladar 直视 Down-looking 重采样 Resampling 姿态补偿 Attitudes Compensation 惯性导航系统 Inertial Navigation System 机载 Airborne 图像重构 Image reconstruction 最优化 Optimization 自聚焦 Autofocus
其他题名	Research on the Synthetic Aperture Imaging Ladar image reconstruction and post-processing technologies
英文摘要	合成孔径激光成像雷达（Synthetic Aperture Imaging Ladar，简称SAIL）是从微波波段的合成孔径雷达（Synthetic Aperture Radar，简称SAR）发展而来的一种成像雷达形式，是一种通过相干技术，利用运动孔径合成原理实现远距离、高分辨的成像观测手段，具有全天候、全天时、远距离、高分辨等优点。在军事、航天遥感、机载遥感、海洋陆地监测等领域具有广泛的应用价值。目前为止，主要发展了两种合成孔径激光成像雷达模式：利用测距原理及多普勒效应进行成像的侧视合成孔径激光成像雷达，和利用空间光相位调制原理进行成像的直视合成孔径激光成像雷达。侧视体制合成孔径激光成像雷达采用本振光与信号光混频的接收方式，这种情况下大气的扰动对雷达成像影响较大；为了实现方位向的良好成像，需要保证方位向初始相位的稳定，即触发位置选择在发射信号频率的固定位置，但在实际应用中，由于发射信号频率的漂移、噪声等原因，实现起来相对困难；侧视SAIL中目标处成像光斑的大小以及系统的方位向分辨率都是由雷达天线口径决定的，由衍射光学原理可知，小的天线口径经过衍射之后，形成的目标处光斑较大，所以为了增大成像视场，需要小的天线口径；但是天线口径的减小又会影响接收信号的能量，降低接收信噪比，所以侧视SAIL在应用时要综合上述因素，这在某种程度上影响了侧视SAIL的工程实用化。 直视SAIL的成像原理利用自由空间波前变换技术和光学调制技术，通过发射两束同轴同心正交偏振的光束，采用自差接收方式，可以有效的克服大气湍流等影响。这种雷达体制充分的发挥了光学优势，降低了系统的复杂度，为解决合成孔径激光成像雷达工程化难题提供了一种有效的解决途径。 为了满足机载直视SAIL高速成像的要求，需要一种自由空间波前相位调制模块来满足高速调制要求。同时，雷达平台的运动轨迹很容易受到大气扰动、飞行姿态改变等因素的影响进而使雷达载体轨迹偏离理想直线。因此，基于惯性导航系统参数的运动补偿便成为了获得良好聚焦图像的一个重要前提。另一方面，要实现精确的运动补偿就必须拥有高精度的雷达位置、姿态信息。然而在大多数情况下，装配的导航装置并不能提供符合精度和稳定性要求的运动参数，同时由于大气湍流等非可测量因素对成像的影响，必须开发基于回波数据的误差估计和补偿方法，即图像的后处理研究。 本文在直视SAIL的基础上，围绕高速直视SAIL系统设计、图像重构及图像后处理展开了深入的研究，所做的主要工作及创新如下： （1）针对直视SAIL等高速成像的要求，提出了具有自补偿功能的高速直视合成孔径激光成像雷达相位调制模块设计，完成了相关实验，验证了模块的可行性、可靠性。该模块可以对两束同轴同心偏振正交的光束进行了二维空间波面调制，其中，通过高速振镜对交轨向相位进行正弦调制，通过曲率半径相反的柱面镜实现对顺轨向的空间二次项相位调制。 （2）为了实现直视SAIL高速成像的要求，交轨向的相位调制模块采用往返正弦调制方式。相较于理想的线性往返调制，可以达到很高的调制速度，同时可以避免相位调制模块高速线性调制状态下急起急停对硬件的损伤。针对此种情况，基于重采样原理，提出了交轨向非线性补偿算法，这部分为直视SAIL的高速成像提供了前提。 （3）针对机载直视SAIL的情况，系统的分析了机载情况下坐标系的转化关系，以及飞机飞行姿态（偏航，俯仰，翻滚，平移）和飞行轨迹（三轴平移和三轴速度）的改变对于雷达成像的影响，给出了一维仿真结果，验证了影响分析的正确性；基于惯性导航系统的参数提出了一套运动补偿算法，进行了模拟仿真，并于2016年7月份进行的3km机载实验中验证了算法的正确性和可行性。 （4）开展了直视逆SAIL的远场试验验证，成像距离达到了1.8km和3.4km，获得了理想的分辨率，清晰的成像结果，对以后在战略防御、反卫星、战术武器以及雷达天文学中有着重要的应用价值。 （5）对目前SAR的图像自聚焦算法进行了系统的分析，其中重点分析了基于图像参数（锐化函数，熵等）自聚焦算法，提出了一种基于遗传算法的最大锐度算法，该算法可以在求取相位误差的过程中忽略初始值的影响，实现全局最优化。; Synthetic Aperture laser Imaging Ladar (SAIL), whose principle was come from the Synthetic Aperture Radar(SAR) in the radiofrequency domain, was a kind of imaging observation way that using the coherence technology and the aperture synthetic principle to realize the long distance, high resolution imaging, and has the advantages of all-weather, all-day, long distance and high resolution imaging. In the military, remote sensing, airborne remote sensing, ocean and land monitoring, and some other fields, it has extensive application value. So far, it has been developed two kinds of synthetic aperture imaging ladar: side-looking synthetic aperture imaging ladar, which is imaged using ranging and Doppler effects, and down-looking synthetic aperture imaging ladar, which is imaged through space optical phase modulation principle. Side-looking SAIL, which was received by optical heterodyne between local light and signal light, was greatly affected by atmospheric disturbances; in order to ensure undisturbed quadratic phase history in azimuthal direction, the initial phase of frequency signal is required to be strictly synchronized, which is mean that the trigger position is triggered at the fixed position of the transmitting signal frequency. This is relatively difficult to realize in practical application because of the drift and noise of the transmitting signal frequency; the light spot size and imaging resolution is decided by the transmitting aperture in side-looking SAIL, known from the principle of diffraction optics, a smaller diameter optical antenna aperture is needed in order to increase the illuminated spot in the target plane，which means to increase the transmitting divergence angle of the SAIL. However, the receive energy will decrease because of the small optical antenna aperture, reduce the signal to noise ratio, so the side-looking SAIL needs to match the transmitting divergence angle and receiving field of view-angle. These factors mentioned above seriously affect the engineering practicality of side-looking SAIL. The down-looking SAIL was based on the key idea of free space wavefront transformation technology and optical modulation technology. The emissive beam was divided into two coaxial and polarization-orthogonal beams，and the autodyne receiving mode was adopted, which can overcome the atmospheric disturbances in a large extent. The down-looking SAIL system has made full use of the optical superiority and reduced the complexity of the system. It provides an effective way to solve the engineering problem of SAIL. In order to meet the requirements of high speed imaging, such as airborne down-looking SAIL, the free space wavefront phase modulation module is required to meet the high speed modulation requirements. At the same time, the trajectory of radar platform was easily affected by the influence of atmospheric disturbances, flight attitudes change and so on, so that the trajectory of radar carrier is deviated from the ideal line. Therefore, the motion compensation based on the parameters of the Inertial Navigation System (INS) has become an important prerequisite for obtaining a good focused image. On the other hand, in order to achieve accurate motion compensation, high precision radar position and attitude information must be possessed. However, in most cases, the navigation device assembly can not provide the movement parameters, which is conforming to the accuracy and stability. At the same time, due to the influence of non-measurable factors on imaging, the estimation and compensation method based on the echo data must be developed, which is the research on image post-processing. This thesis was based on the principle of the down-looking SAIL, centered on the research on high speed SAIL system design, image reconstruction and image post-processing were carried out. The main work and innovation were as follows: (1) For the requirement of high speed imaging in down-looking SAIL, a high speed phase modulation module with self-compensation function is proposed, the feasibility and reliability of the module were verified by the related experiments. This module can perform two dimensional spatial wavefront modulation on two coaxial and polarization-orthogonal beams, in which the spatial phase in orthogonal direction was modulated by the high-speed galvanometer and the phase in the azimuthal direction was modulated by the cylindrical mirrors with opposite curvature radius. (2) For the requirement of high speed imaging, such as down-looking SAIL, the phase modulation module in the orthogonal direction makes a high-speed round-trip sine wave motion. Compared to the linear round-trip modulation under ideal condition, a high modulation speed can be achieved, and the hardware damage of the quick starting and braking under high-speed linear modulation can be avoided. In this case, based on the principle of resampling, a nonlinear compensation algorithm is proposed, which provides the precondition for high-speed imaging of down-looking SAIL. (3) For the airborne down-looking SAIL, the transformation relation of coordinate system under airborne condition is analyzed systematically, and the influences of aircraft attitudes (yaw, pitch, roll and translation) and aircraft trajectory (three axis translation and three axis velocity) changing on imaging are analyzed, a one-dimensional verification result was given and proved the correctness of the influence analysis. Based on the parameters of INS, a motion compensation algorithm is proposed, which is simulated and verified in the 3km airborne experiment in July 2016. (4) A far-field verification for the down-looking inverse SAIL was carried out. The imaging distances are 1.8km and 3.4km. Ideal resolution and clear image results are obtained, which has an important application value in the future in strategic defense, anti-satellite, tactical weapons and radar astronomy. (5) The autofocus algorithm of the SAIL is analyzed systematically. The autofocus algorithms based on image parameters (sharpening function and entropy) are mainly analyzed, and a maximum sharpness algorithm based on genetic algorithm is proposed. The algorithm can ignore the influence of initial value in the process of obtaining phase error and realize global optimization.
学科主题	光学工程
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/31092]
专题	中国科学院上海光学精密机械研究所
作者单位	中国科学院上海光学精密机械研究所
推荐引用方式 GB/T 7714	李光远. 合成孔径激光成像雷达图像重构及后处理技术研究[D].

个性服务

查看访问统计

相关权益政策

暂无数据

收藏/分享

除非特别说明，本系统中所有内容都受版权保护，并保留所有权利。