合成孔径激光成像雷达时空散斑效应研究
文献类型：学位论文
| 作者 | 许倩 |
| 学位类别 | 博士 |
| 答辩日期 | 2014 |
| 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 时空散斑效应 光学接收天线 散斑抑制 目标偏振反射特性 |
| 其他题名 | Research on Space-time Speckle Effect in 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）是微波合成孔径雷达（Synthetic Aperture Radar，简称SAR）在光频段上的应用，是目前能够在远作用距离上实现厘米量级分辨率的最可行的光学成像手段。合成孔径激光成像雷达以高相干近红外激光器为辐射源，在实现更高分辨率的图像的同时不可避免地受到激光固有的散斑效应影响，国内外已报道的SAIL成像实验结果也说明了这一点。对于合成孔径激光成像雷达中散斑效应的研究由美国海军实验室首先提出，主要集中在散斑效应对外差探测信噪比的影响上；对散斑效应如何影响合成孔径激光成像雷达成像，国内外并没有开展相关研究的报道。针对这一问题，本文开展了条带式合成孔径激光成像雷达中的时空散斑效应及其对雷达成像影响的研究。研究内容主要从以下几个方面展开： 1. 条带式合成孔径激光成像雷达时空散斑效应理论分析和数值模拟研究。建立了合成孔径激光成像雷达远场衍射散斑理论模型，理论分析了SAIL中的时空散斑效应；利用Matlab模拟了时空散斑效应的图样分布及其随波长啁啾在距离向上的平移；最后通过大口径SAIL演示样机实验验证了时空散斑效应的距离向波长特性。 2. 合成孔径激光成像雷达散斑的天线接收效应分析。理论分析了接收天线散斑孔径积分场的时空变化特性。利用Matlab模拟了不同天线散斑尺度比、不同天线积分起始位置下的天线积分散斑场分布及其统计特性。 3. 合成孔径激光成像雷达散斑效应对成像影响的理论分析和仿真模拟。建立了完整的散斑效应对SAIL成像影响的理论基础，分析并推导了受散斑效应影响的合成孔径激光成像雷达二维数据收集方程及成像处理过程。利用Matlab模拟了散斑效应对单点和多点目标成像的影响。分析了不同天线散斑尺度比、不同天线积分起点位置散斑效应对成像所需的光电流交流项、距离向压缩和最终分辨单元成像结果的影响。 4. 合成孔径激光成像雷达散斑效应抑制方案设计。提出利用散斑场随啁啾波长在距离向上平移的特性减弱其对SAIL距离向成像的影响。同时提出一种合成孔径激光成像雷达的多孔径光学发射天线系统，可以减弱目标回波激光散斑场强度分布的不均匀性。 5. 目标偏振反射特性测量装置设计。设计了合成孔径激光成像雷达目标偏振反射特性测量装置，提出了在空间上和时间上均化散斑效应的可行性方案。选取十种不同材料的目标，通过实验初步测量了目标斯托克斯参量并得出了目标偏振反射特性与入射角的关系。 本文分析了条带式合成孔径激光成像雷达时空散斑效应基本原理，建立了完整的数学模型，分析了合成孔径激光成像雷达散斑的天线接收效应，进行了合成孔径激光成像雷达散斑效应对成像影响的理论分析和模拟验证实验研究，同时提出了抑制合成孔径激光成像雷达散斑效应的参考方案，初步测量了目标偏振的反射特性，下一步需完整测量斯托克斯参量。同时，对于其他工作模式的合成孔径激光成像雷达的散斑效应本文并未涉及，未来可进一步开展研究。 |
| 英文摘要 | The concept of synthetic aperture imaging ladar (SAIL) arises from microwave synthetic aperture radar (SAR) techniques. SAIL can theoretically obtain centimeter-class resolution using a small-diameter optical real aperture when the ladar is at a distance of more than thousands of kilometers. Given that a near-infrared laser signal is always adopted as the transmitting signal, SAIL is inevitably influenced by speckle effect because of the coherence of the laser. Several SAIL two-dimensional (2D) reconstructed images reported by different institutes are degraded by laser speckle effect. Research on speckle effect in SAILs was first presented by the Naval Research Laboratory. They have shown the impact of SAIL speckle effect on signal-to-noise ratio (SNR) in photon-limited heterodyne detection. However, the influences of speckle effect to the SAIL image quality have not been reported. Based on the theory analysis and simulation results, research on the space-time varying speckle effects in a strip mode synthetic aperture imaging ladar was carried out. In this paper, we mainly discuss this effect in the following aspects: 1. Research of temporally and spatially varying speckle effects based on the strip mode synthetic aperture imaging ladar. Established the physical model of the SAIL system in the far field diffraction region, and analyzed the temporally and spatially varying speckle effects in SAIL; Carried out the numerical simulations of speckle patterns and their motion in the range direction, validated the experiment of speckle wavelength property by using the SAIL experimental model system. 2. Analysis of the receiving characteristics of integrated speckle. Investigated the temporally and spatially varying integrated speckle characteristics theoretically; performed the simulation of the statistic characteristics of the speckle field integrated by the receiving antenna with different scales and locations. 3. Theoretical analysis and simulations of the influence of the space-time speckle effect on the image quality. Analyzed the complete physical and mathematical models of space-time speckle effects and their influence on images acquired by the strip mode SAIL. Deduced the 2D data collection and imaging process of SAIL taking speckle effect into consideration; Simulated the influence of speckle effect on a resolution element and multiple resolution elements. Analyzed the influence of antenna-integrated speckle to the beat frequency photocurrent, the range pulse compression and the azimuth imaging. 4. Investigation and simulation of speckle mitigation schemes. Proposed a new speckle-reduction method based on the wavelength characteristics of the speckle effect to improve the SAIL image quality; Designed a multi-channel transmitter structure to enhance the uniformity of speckle echo. 5. Design and optimization of the reflection characteristics measuring system based on speckle homogenization. Performed the Stokes parameters measurement of 10 different materials; calculated the relation between the reflection characteristics and the observation angle. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15881]  |
| 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 | 许倩. 合成孔径激光成像雷达时空散斑效应研究[D]. 中国科学院上海光学精密机械研究所. 2014. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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