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题名:
基于扩展信标的数值仿真研究
作者: 林辉轮
学位类别: 博士
答辩日期: 2007-06-13
授予单位: 中国科学院光电技术研究所
授予地点: 光电技术研究所
导师: 姜文汉
关键词: 自适应光学 ; 扩展信标 ; 非等晕误差 ; 数值模拟
其他题名: numerical simulation of adaptive optics with extended beacons
学位专业: 信号与信息处理
中文摘要: 自适应光学作为一种克服大气湍流效应对光学系统性能影响的有效手段,在许多领域已经得到了成功应用,但这需要一个“点源”作为信标。然而在实际应用中,真正的点源很难获得,常常容易得到的是扩展信标。许多研究都表明,扩 展信标的非等晕性会降低自适应光学系统的性能,因而扩展信标成为自适应光学领域关注的一个非常重要的问题。本文旨在建立一个扩展信标聚焦光束大气传输自适应光学校正的数值仿真实验平台,并在此基础上开展扩展信标非等晕性对聚焦光束大气传输校正效果影响的定量研究。 论文首先从扩展信标激光传输式自适应光学系统的工作原理出发,研究了扩展信标自适应光学校正所涉及的相关物理基础,包括扩展信标源、大气湍流效应对激光传输的影响和自适应光学相位校正。进而提出了仿真平台的三大构件,即:扩展信标源模拟、激光大气传输模拟、波前探测模拟,并对三大模块的数值仿真方法分别进行了深入的研究。 在扩展信标源模拟方面,针对扩展信标的特点和自适应光学对信标的要求从扩展信标本质的本质出发,把整个信标看作由点构成,采用逐点方式来模拟。 在激光大气传输模拟方面,研究了激光大气传输方程,根据方程解的形式,采用多相屏模型来模拟激光大气传输,将激光大气传输分为真空衍射与大气畸变两部分。对于真空衍射,详细讨论了衍射积分法、傅立叶光学法、有限差分法和 离散傅立叶法。在综合上述方法的计算精度、计算量及实现难易程度的基础上,选用快速傅立叶法模拟激光真空传输。对于大气畸变作用,关键在于模拟大气相屏,为此详细讨论了FFT 谱反演法、Zernike 多项式法和分形相屏法三种大气相 屏的数值模拟方法。结果表明,分形相屏法精度高,计算量小。因此,本文在仿真平台中采用离散傅立叶法和分形相屏法模拟激光大气传输。 在波前探测模拟方面,对比研究了横向剪切干涉法、曲率传感器法和Hartmann 传感器法的基本原理及其波前复原的特点,根据大气湍流效应时间、空间特性及仿真平台对波前探测精度的要求,选择Hartmann 作为仿真平台中的波前探测方法。在哈特曼的模拟中,提出了一种新的数值模拟方法,有效地减小计算误差,降低了计算量。 在上述工作的基础上,建立了仿真平台。随后对扩展信标条件下,聚焦光束大气传输校正的相关问题进行了仿真研究,主要包括扩展信标的非等晕误差及信标扩展对激光大气传输校正效果的影响两部分。通过对扩展信标非等晕误差的仿真,验证了前人的研究成果,获得了非等晕误差的定量关系;在信标扩展对激光大气传输校正的影响方面,开展了不同场景条件下扩展信标对激光传输自适应光学校正效果影响的研究。 本文围绕扩展信标聚焦光束大气传输自适应光学校正问题进行了深入的研究,建立了从信标源到校正效果分析的数值仿真平台,开展了扩展信标条件下聚焦光束大气传输自适应光学校正相关问题的数值仿真研究,获得了部分定量结果,为相关研究工作奠定了良好的基础。
英文摘要: Adaptive optics(AO) is a technique that corrects in real-time for phase aberrations in an optical system. AO works in many areas , including astronomical telescopes and laser transmission. All these systems use a point-source to measure the distortion induced by atmospheric turbulence. There are many interesting cases where the use of AO is desirable, but no point source is available. As a matter of fact, only extended source is available in most of the interesting scenarios. Due to the anisoplanatic effects produced by the extended source, the performance of AO system degrades. The purpose of this Ph D dissertation is to establish a simulation platform of an AO system with laser propagation in the atmosphere based on extended beacons and to do some research about the anisoplanatism from extended beacon on the platform. Based on the principle of the AO system with extended beacon for laser transmission, the relevant physical problems of the system are discussed, including extended beacon, atmospheric turbulence effects on laser transmission and the AO system. According to the system, the simulation platform consists of extended beacon module, laser atmospheric transmission module and wavefront detection module. The numerical methods of the three modules are studied in depth. Firstly,the numerical simulation of extended beacons is studied. According to the characteristics of the extended beacon and the requirement of AO system, the extended beacon is simulated by point-to-point. Secondly, numerical simulation of laser propagation in the atmosphere is investigated. According to the form of the solution to the parabolic equation,muti-phasescreen method applies to simulate laser transmission in the atmosphere. The significant characteristic of this method is to spit the wave propagation in the atmosphere into the problem of free diffraction and the problem of refraction. For free diffraction, the diffraction integral method, the Fourier optics method, the finite difference method and the discrete Fourier method are discussed. Considering amount of the computation and convenience of implementation, the discrete Fourier is used to simulate free diffraction. To solve the problem of the refraction, the methods for generation of random phase screen are studied. The power spectrum method based on fast fourier transform (FFT), zernike polynomial method and fraction phase-screen method are compared and it shows that fraction phase-screen method needs relative small amount of computation and has high accuracy. Taking amount of computation and simulation accuracy into account, the simulation platform simulates phase-screen with fractional phasecreen method. Consequently, laser atmospheric transmission is simulated with discrete Fourier method together with fraction phase-screen method. Further more, parameters about the wave propagation in random medial are discussed. Thirdly, the numerical simulation of wavefront detection is studied. The shearing interferometry, curvature sensor and Hartmann wave-front sensor are discussed and the characteristics of the three wavefront sensor are summarized. Considering the characteristic of atmosphere , the Shack-Hartmann wave-front sensor is used in the platform. The investigation is conduct in numerical simulation of Shack-Hartmann wavefront sensor. A new method is presented , and this method simplifies the computational process and reduces the amount of computation. The Shack-Hartmann wavefront sensor is simulated with two means and some examples are performed to test the module. Based on aforementioned work, a simulation platform is established and the platform proves to be reliable. On the platform, some issues about extended beacons were studied, including the anisoplanatism error of the extend beacons and the influence of the extended beacons on beam-projection correction. As for the anisoplanatism error of extend beacons, the simulation results are consistent with previous results. In the dissertation, a simulation platform for extended beacon is established and some quantitative results are obtained through simulation studies. This work, in one hand, provides some reference and basis for practical application. On the other hand,it provides a reliable simulation platform for further study.
语种: 中文
内容类型: 学位论文
URI标识: http://ir.ioe.ac.cn/handle/181551/229
Appears in Collections:光电技术研究所博硕士论文_学位论文

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Recommended Citation:
林辉轮. 基于扩展信标的数值仿真研究[D]. 光电技术研究所. 中国科学院光电技术研究所. 2007.
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