论文标题:等离子体羽流场的光学全息干涉度量技术研究
Diagnosing Microwave Plasma Thruster"s Plume by Holographic Interferometry
论文作者 冯伟
论文导师 李恩普,论文学位 硕士,论文专业 光学
论文单位 西北工业大学,点击次数 143,论文页数 68页File Size8253k
2005-03-01论文网 http://www.lw23.com/lunwen_809232/ 全息干涉;数字全息术;相位倍增;微波等离子体推进器;羽流场;电子数密度;MATLAB
Holography interferometry; digital holography; phase multiplication; Microwave Plasma Thruster; Plume"s field; Electron density; MATLAB
电推进中的微波等离子推进器(Microwave Plasma Thruster,简称MPT)由于具有比冲高、寿命长、体积小和污染轻等优点而广泛地引起航天器界的重视,针对其羽流场的检测成了至关重要的一部分。由于光学全息干涉计量术是一种可以对三维形变和位移过程进行可视化全场测量的光学检测方法,且具有全场、非接触、测量精度高以及不受测量物体自发光影响等优点,在等离子体羽流场的检测中具有非常重要的意义。本文从理论和实验两部分探讨了全息干涉术及数字全息术对MPT羽流场的检测,并利用计算机模拟了干涉条纹,验证了实验的结果。主要内容包括:(1) 概述了传统全息术及数字全息术的历史、发展、现状及优点,介绍了等离子体推进器的基本知识和等离子体诊断的各种方法。针对等离子体羽流检测提出了利用光学检测的优势以及可行性。(2) 介绍了全息干涉计量术的理论基础,通过公式推导了二次曝光干涉术的测量原理,并进一步介绍了数字全息术的记录以及再现原理。接着介绍了数字全息术再现的数学基础--离散傅里叶变换,详细阐述了数字全息图的记录与再现的基本原理。利用MATLAB编写了相应的程序,对记录的数字全息图进行分析处理。最后,给出了全息干涉术检测等离子体的理论基础。(3) 分别利用马赫--曾德干涉装置、二次曝光干涉法及实时全息法等观察了等离子体羽流场对光程的影响,都获得了基本相同的结果;通过二次曝光实验记录了等离子体羽流场的全息干涉图。接着利用数字全息干涉术记录了数字全息干涉图,通过程序处理直接得到相位差,由此计算出羽流场的电子数密度;并通过相位倍增,增加了干涉条纹的密度,全场观察了条纹变化。在光学平台实验的基础上,针对真空箱中的特殊条件,设计了两套光路,可以在真空箱中进行全息干涉检测。(4) 介绍了MATLAB语言的基础知识,MATLAB实现光波波前以及实现光波的线性传输的方法,并通过编写程序对各种不同的等离子体模型进行模拟,得到了柱状、球状及锥体时候的干涉图像,并可以在干涉图像中加入参考干涉条纹,可以直接得出相位差。并利用MATLAB编写了程序界面,可以方便的操作和运用。
Microwave Plasma Thruster(MPT) of Electron thruster has so many advantages, such as high specific impulse, long longevity, small cubage and little pollution, it thus is attached great importance by astronautics to diagnose the plume. As holography interferometry has more outstanding strongpoints and better advantages for phasic field, such as all field, noncontact, and high precision and non-disturbance by plasma luminescence, it is an effective means in the plasma number density of electronic diagnosis and is very meaningful in diagnosing the MPT"s plume. This dissertation has probed into diagnosing the MPT"s plume of holographic interferometry and digital holographic from two pare of the fundamental theory and experiment , and the intervened stripe simulated by MATLAB program; two setups are designed to diagnose the MPT"s plume in the vacuum box. The main content is as follows:(1) History, evolution, status quo and advantage of holographic and digital holographic are summarized, the basic information of MPT and methods of diagnosing plasma is presented. It is shown that the optical diagnosing plasma is an effective method for diagnosing MPT plasma"s plume.(2) Foundation theory of holographic interferometry is presented, theory of double-exposed holographic interferometry is deduced by formula, and theory of recording and reappearance digital holography is introduced. Analytical foundations for numerical reconstruction of digital holography, namely discrete Fourier transform theory, is also showed in this dissertation. Digital holography is analyzed by MATLAB program. Lastly, the foundation theory of interferometry diagnosing plasma is presented.(3) Optical distance disturbed by the plasma"s plume field is observed by Mach-Zehnder interference, double-exposed holography, and real time holography—all get the similar result. Holographic of the plasma"s plume is recorded by double-exposed holographic experimentation, picture of digital holography is recorded by digital holographic interferometry, and phasic difference is directly gained by numerically reconstructing, from which the electron density is also calculated. By employing the phase multiplication method, the fringe density of the interference pattern obtained by digital hologram was multiplied to reveal the refractive index distribution of the plume field more intuitively. Base on the experiment on the optical table, two setups are designed to diagnose plume in vacuum box.(4) Foundation information of MATLAB program is presented. Light wave front and light wave linearity transfer are simulated by using MATLAB. And the pole, globosity and cone plasma field interference figures are simulated by MATLAB, and reference fringe is added to the interference. Graph user interface is programmed for the simulation of the optical experiment.
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