合成孔径激光成像雷达的实时光学图像重构研究
文献类型：学位论文
| 作者 | 孙志伟 |
| 学位类别 | 博士 |
| 答辩日期 | 2015 |
| 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 | 合成孔径激光成像雷达 光学成像处理 二维傅里叶变换 液晶空间光调制器 球面透镜 柱面透镜 像散透镜 菲涅耳衍射 低通滤波 全息记录 热固定 衍射效率 Fe:LiNbO3晶体 波面记录 |
| 其他题名 | Research on Real-time Optical Image Reconstruction for Synthetic Aperture Imaging Ladar |
| 中文摘要 | 合成孔径激光成像雷达（Synthetic Aperture Imaging Ladar，简称SAIL）基本原理来源于微波波段的合成孔径雷达（Synthetic Aperture Radar，简称SAR），是国外报道的能够在上千公里观察距离上实现厘米量级分辨率的唯一光学成像观测手段。在20世纪60年代和70年代，光学信息处理最成功的应用之一就是对微波SAR回波数据的成像处理，伴随着数字处理能力的提高，这种光学处理方法很大程度上被数字处理方式取代。然而随着未来对机载和星载SAIL图像分辨率要求的提高以及实时成像处理的需求，对数字成像处理器的传输和运算速度提出了严峻的挑战。光学成像处理器能够提供高速非相干的数据并行处理能力，从而实现实时图像信息获取，并具有很高的动态输出范围，可以降低对通信系统传输数据量和传输带宽的要求，另外，可以实现集成化，减小系统的重量和体积，降低系统功耗，因此在未来合成孔径激光成像雷达的数据成像处理中具有很大优势。目前微波SAR的光学处理器已经取得了很大进展，紧凑结构的实时SAR光学处理器已经研制成功并应用，但是目前国际上对SAIL的光学成像处理尚处于初级研究阶段，具有较高的研究价值和发展空间。本文围绕SAIL的光学成像处理，开展了相关理论及实验研究，主要内容包括： 1.提出了一种合成孔径激光成像雷达的二维傅里叶变换成像算法，给出了算法的基本流程及其物理描述，并与SAIL传统成像算法进行了对比，结合侧视SAIL单散射体目标两维数据收集方程对SAIL二维傅里叶变换算法进行了详细的解析式推导，并得出了矩形天线孔径结构下的距离向、方位向成像分辨率，并提出了适合SAIL二维傅里叶变换算法的两种处理模式，即一维输出模式与两维输出模式，最后给出了SAIL二维傅里叶变换算法与SAIL传统成像算法对SAIL大口径实验室验证装置所得目标回波数据的成像处理结果及其各自处理时间对比。 2.提出了一种基于两维傅里叶变换的SAIL光学处理器。首先介绍了该光学处理器的原理方案，结合SAIL单散射体目标两维数据收集方程对光学处理器的成像过程进行了解析式分析，并给出了光学处理器的成像分辨率，定义了成像宽度，给出了成像压缩比，并确定了保持目标面貌比例的数值关系，结合现有设备搭建了一套SAIL光学处理器实验室验证装置并给出了该装置应用前述两种处理模式对SAIL大口径实验室验证装置所得目标回波信号的成像处理结果。 3.提出了一种基于单个实像散透镜的合成孔径激光成像雷达光学成像处理器，根据液晶空间光调制器的具体类型，给出了透射式与反射式两种结构。基于侧视SAIL与直视SAIL的统一数据收集方程对光学处理器的成像过程进行了解析式分析，确定了结构参数关系，得到了成像分辨率、目标成像压缩比等性能参数。分析结果表明，在特定参数条件下，像散透镜可简化为柱面透镜。应用现有设备搭建了一套基于单个柱面透镜的SAIL光学成像处理器，并进行了实验验证，给出了该处理器对SAIL大口径实验室验证装置所得目标回波数据的成像处理结果。 4.提出了一种基于单个虚柱面透镜的合成孔径激光成像雷达的光学处理器。基于侧视条带模式SAIL两维数据收集方程对成像重建过程进行了理论分析，给出了目标成像压缩比，特别给出了矩形以及圆形天线孔径下的成像分辨率。另外，分析了由LCSLM决定的SAIL等效采样率以及LCSLM的等效焦距的取值范围。基于上述理论分析，利用现有设备，搭建了一套SAIL虚柱面透镜光学处理器实验室验证装置，并进行了实验验证，给出了该处理器对SAIL大口径验证装置所得目标回波数据的像重建结果。 5.提出了一种合成孔径激光成像雷达两维匹配滤波成像算法，用于对采用单频本振光与线性调频信号光进行外差接收所得的回波信号进行成像处理。首先给出了侧视条带模式下的单点目标两维数据收集方程，对上述成像算法进行了数学描述，具体分析了矩形与圆形孔径的成像分辨率。利用此算法对模拟SAIL目标回波信号进行了成像处理。 6.提出了一种用于直视SAIL的集成化光学处理器，首先给出了光学处理器的基本原理方案，然后结合直视SAIL两维数据收集方程对成像过程进行了解析式分析，给出了成像分辨率、成像压缩比等特征参数，基于现有设备，搭建了一套直视SAIL光学处理器样机，给出了样机的具体结构参数，并给出了该样机对直视SAIL实验室验证装置所得回波数据的成像处理结果。 7.提出了一种用于合成孔径激光成像雷达的光折变全息并行成像处理器。首先介绍了全息记录/热固定的物理机制，然后对现有的不同掺杂浓度、不同厚度的Fe:LiNbO3晶体进行了单偏振以及双偏振均匀性测定，并测定了晶体的平整度，对相同厚度，不同掺杂浓度的Fe:LiNbO3晶体在同等条件下进行了全息记录及热固定衍射效率对比试验，另外，对Fe:LiNbO3晶体进行了波面的全息记录以热固定，并对晶体内记录的波面进行了检测，最后，利用记录波面后的Fe:LiNbO3晶体进行了SAIL光学像重建实验并给出了实验结果。 |
| 英文摘要 | The foundations of synthetic aperture imaging ladar (SAIL) come from synthetic aperture radar (SAR) in microwave region. SAIL can provide centimeter-class resolution with an aperture no larger than a few meters on an observation distance of thousand kilometers or more. Optical techniques are considerably successful in the processing of data obtained by SAR when the digital computing power for SAR image reconstruction is not available. Furthermore, researchers’ interest is still focused on optical techniques in SAR data processing because of their inherent advantages, such as parallel and ultra-fast computing capability. Recently, a compact real-time optical processor for satellite-borne SAR systems has been successfully developed and tested. SAIL systems typically generate large amounts of data in the form of complex value that are difficult to compress digitally. Specifically, for the future on-board and satellite-borne SAIL systems, this is a clear disadvantage. In this paper, the issue of optical image reconstruction for SAIL is detailed analyzed in the following aspects: 1. A two-dimensional (2D) Fourier transform imaging algorithm for SAIL is proposed. The procedure and physical description of this algorithm are presented. The imaging process is mathematically analyzed by virtue of 2D data collection equation of strip-mode side-looking SAIL. The imaging resolutions of rectangular and circular antenna are presented. Two processing modes suitable for this algorithm are suggested. The imaging result of this algorithm for practical data collected from one SAIL demonstrator is given. 2. Based on the SAIL 2D Fourier transform imaging algorithm, a principle scheme of optical processor based on 2D Fourier transform is proposed. The imaging process is mathematically analyzed using 2D data collection equation of strip-mode side-looking SAIL. Imaging resolution and imaging width of the optical processor are given, as well as the target image compression ratio. To verify this principle scheme, an experimental optical SAIL processor setup is constructed. The imaging result of SAIL data obtained by one SAIL demonstrator is also presented. 3. One principle scheme of optical processor for SAIL using one real astigmatic lens is proposed. Two structures of reflecting and transmission are presented. The imaging process is mathematically described using the unified data-collection equation of side-looking and down-looking SAILs, with emphasis on parameter relations, imaging resolutions and compression ratios. Results also show that under certain circumstances, the astigmatic lens can be specialized into a cylindrical lens. The experimental setup is constructed and the imaging result is also presented. Based on the MATLAB, an auto control software for SAIL optical processor is coded to control the SAIL data reading, preprocessing, and loading, as well as image capture, cutting out and joint then ultimately store and display the target image. 4. A principle scheme of optical SAIL processor based on one virtual cylindrical lens is proposed. SAIL raw data are initially digitally added with quadratic phase in the range direction. These data are then uploaded to a liquid crystal spatial light modulator (LCSLM) to modulate the incident plane wave. A target image is achieved through 2D free-space Fresnel diffraction. A full mathematical formulation on the imaging reconstruction based on the data-collection equation of strip-mode side-looking SAIL is given. The imaging resolutions and target-image compression ratios are investigated. The laboratory experimental demonstrations and imaging result are presented. 5. A two-dimensional matched filtering imaging algorithm for synthetic aperture imaging ladar is proposed. This algorithm simultaneously performs quadratic phase matched filtering in range and azimuth direction for the data obtained through heterodyne detection with single frequency local oscillator to achieve target image. The SAIL 2D data-collection equation of point target through heterodyne detection with single frequency local oscillator is presented. Imaging process of this algorithm is mathematically analyzed. Imaging resolutions of this algorithm for the SAIL with rectangular and circular apertures are described specificaly. Imaging result of simulated SAIL data is presented. 6. A compact optical processor for down-looking SAIL is designed. The imaging process of this optical processor is mathematically described. The characteristic parameters such as imaging resolution and target image compression are presented. One down-looking SAIL optical processor demonstrator is constructed and imaging result of data collected from one down-looking SAIL demonstrator is given. 7. A principle scheme of optical SAIL processor based on holography using photorefractive crystal is proposed. The physical scheme of holographic recording and thermal fixing is given. The uniformity of single-polarization and double-polarization for Fe:LiNbO3 crystals of different doping density and thickness is tested as well as the crystals’ parallelism. The experiment of holographic recording and thermal fixing for crystals of different thickness is performed. The wavefront for SAIL target image reconstruction is successfully recorded in Fe:LiNbO3 crystal through holographic recording and thermal fixing. The experiment of SAIL target image reconstruction using the Fe:LiNbO3 crystal after the wavefront recording is conducted and the image result is presented. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15929]  |
| 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 | 孙志伟. 合成孔径激光成像雷达的实时光学图像重构研究[D]. 中国科学院上海光学精密机械研究所. 2015. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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