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chi20181130上海光机所孙建锋557446Synthetic aperture imaging ladar (SAIL) originates from synthetic aperture radar (SAR), which can achieve high resolution imaging by using synthetic aperture technology. It must work in side-looking condition, which is called side-looking SAIL. Side-looking SAIL requires the hydrogen cyanide spectral filter to ensure the initial phase of the beat signal is strictly synchronized. A narrow footprint is inherent to side-looking SAIL. The phase interferences from atmospheric turbulence and mechanical trembling in environments will seriously affect and even destroy the imaging. The down-looking SAIL with a transmitter of two coaxial and orthogonal-polarization beams, and a receiver of self-heterodyne detection, self-heterodynes two polarization-orthogonal signals to eliminate the phase disturbance caused by atmospheric turbulence and mechanical trembling, significantly relaxes the difficulties in side-looking SAIL, The experiment of down-looking SAIL in outdoor and airborne was reported. However, the echo signal is weak during the far-distance imaging in down-looking SAIL, and the laser power is limited, the laser with high power can damage the optical components. Self-heterodyne detection has extremely low signal-to-noise ratio (SNR) when echo signal is weak. Thus, the down-looking SAIL is limited in far-distance imaging. In this thesis, the enhanced self-heterodyne SAIL is proposed, which with a transmitter of two coaxial and orthogonal-polarization beams, whereas with a heterodyne receiver instead of self-heterodyne detection. In the process of digital signal processing, the enhanced self-heterodyne SAIL self-heterodynes two polarization-orthogonal signals to eliminate the phase disturbance caused by atmospheric turbulence and mechanical trembling. The most work can be presented as: (1) We mathematically detailed the principle of enhanced self-heterodyne SAIL and presented the experiments for single point and two dimensional target. We compared the SNR of the point target final image in the enhanced self-heterodyne SAIL system and in down-looking SAIL. The point target final image has a higher SNR and is clearer than that in the down-looking SAIL. (2) The key technologies of enhanced self-heterodyne SAIL are analyzed in detail, including photodetector, technology of high-precision phase digitized simultaneously, and optical hybrid, and the design process and examples are given. (3) We mathematically detailed the imaging process of ghost image, which is generated by the movement of cylindrical lenses in transmitter and relative movement of target and ladar platform. Methods for eliminating ghost image are proposed. The enhanced self-heterodyne SAIL is necessarily work in spotlight mode, and the spatial quadratic phase history in travel direction is generated by the modulation of inner optical fields in transmitter.2019atalunwen21912716135447Synthetic aperture imaging ladar;Down-looking synthetic aperture imaging ladar;Ghost image;Photodetector; Beam scanning trigger; Optical hybridResearch on Enhanced Self-heterodyne Synthetic Aperture Imaging Lidar本振增强同光路双光束光学SAR技术研究合成孔径激光成像雷达(SAIL)来源于微波合成孔径雷达(SAR),是一种采用合成孔径技术的高分辨成像激光雷达,只需要较小的光学孔径就可以实现高分辨成像。SAIL其工作过程必须以侧视为必要条件,即侧视SAIL,需要采用氰化氢光谱滤波触发技术保证拍频信号的初始相位严格同步,光学足趾较小,发射单束激光并外差接收,受大气扰动、运动平台振动、目标散斑和激光雷达系统本身相位变化等影响很大。针对侧视SAIL存在的技术难题,刘立人研究员提出直视SAIL理论,采用波前变换原理对目标投射两个同轴同心且偏振正交的光束并且自差接收。直视SAIL由于采用了同轴光束自差接收,大大降低了大气扰动、运动平台振动、目标散斑和激光雷达系统本身相位变化的影响,光学足趾与成像分辨率在设计时有很大的控制和调制范围,该成像方式在外场和机载实验中对远距离目标成功进行了高分辨成像。直视SAIL虽然能够有效抑制大气扰动、运动平台振动、目标散斑和激光雷达系统本身相位变化的影响,但是由于采用自差接收,在对远距离目标成像时,回波信号弱,易受背景光干扰,自差接收信噪比较低,对直视SAIL发射接收系统要求过高。 本论文针对直视SAIL存在的上述问题,论述了本振增强同光路双光束光学SAR技术,该技术发射正交偏振同光路双光束激光,采用外差接收方式接收回波信号以提高接收信噪比,在数据处理过程中消除双光束激光传播过程中共同经历的相位扰动。研究内容主要包括以下三个方面: (1)研究了本振增强同光路双光束光学SAR技术,对该系统的成像过程进行了详细的论述,并对单点和二维目标进行成像实验。在相同激光出射功率条件下,比较了本振增强同光路双光束光学SAR与直视SAIL对单点目标成像信噪比,可以得出本振增强同光路双光束光学SAR的成像结果更清晰,信噪比更高。 (2)研究了本振增强同光路双光束光学SAR中的关键技术,包括光电探测技术、高精度相位同步技术和本振增强光学复数化接收技术,并给出相应的设计过程和实例。 (3)论述了本振增强同光路双光束光学SAR中鬼像的成像过程,包括内光场调制产生鬼像以及雷达平台与目标相对运动产生鬼像,并给出相应消除鬼像的措施,提出本振增强同光路双光束光学SAR需要工作于聚束模式,通过控制发射装置内柱面镜仅对两束偏振正交的信号光中的一束在交轨向和顺轨向均进行调制,从而实现交轨向扫描和顺轨向孔径合成。合成孔径激光成像雷达;直视合成孔径激光成像雷达;鬼像;光电探测器;扫描角度触发;光学复数化中国科学院上海光学精密机械研究所张国光学工程博士
中文题目: 本振增强同光路双光束光学SAR技术研究
外文题目: Research on Enhanced Self-heterodyne Synthetic Aperture Imaging Lidar
作者: 张国
导师姓名: 孙建锋
学位授予机构: 中国科学院上海光学精密机械研究所
答辩时间: 20181130
中文关键词:
合成孔径激光成像雷达;直视合成孔径激光成像雷达;鬼像;光电探测器;扫描角度触发;光学复数化
英文关键词:
Synthetic aperture imaging ladar;Down-looking synthetic aperture imaging ladar;Ghost image;Photodetector; Beam scanning trigger; Optical hybrid
中文摘要:
英文摘要:
文献类型:学位论文
学位级别: 博士
正文语种: chi
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