| 题名 | 基于皮秒测量平台的光路准直技术与脉宽图像处理算法 |
| 作者 | 秦海棠 |
| 学位类别 | 硕士 |
| 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 | 刘代中 |
| 关键词 | 高功率激光 准直技术 皮秒测量 缩束单元 脉宽图像 |
| 其他题名 | The alignment technique and processing algorithms of pulse width image based on picosecond measurement platform |
| 中文摘要 | 高功率激光驱动装置包含许多分系统和组件，其是用于惯性约束核聚变（ICF）的研究。光路的自动准直是一个关键的子系统，它能够保证激光装置高效的运行，已成为不可或缺的一部分。皮秒测量平台是针对拍瓦激光装置研制的测量系统，能够提供相关参数的测量和分析，如能量、脉宽、远场、信噪比等。目前的难点和热点在于单次脉冲信噪比的诊断与优化。并且，单次脉冲的高动态范围信噪比的测量是一个世界性的技术难题。 为了解决新型的单脉冲信噪比测量仪在线精密光路调试困难的问题，本文首次将光路的自动准直技术引入到皮秒测量平台。其次，利用准直系统的近远场单元技术成功验证了带有衰减功能的双通道缩束皮秒测量系统的可行性，成功地实现皮秒测量平台的大小能量测量通道的自动切换。另外，为了提高皮秒测量平台上脉宽测量的精度和效率，利用图像处理技术和软件编程实现了脉宽的在线实时测量。 具体有以下几方面的内容： 第一，提出了立体空间激光光路的准直算法，即4×4维线性矩阵的数学模型。 为了满足新型的单脉冲信噪比测量仪中周期性极化铌酸锂（PPLN）晶体对光束偏振态的要求，皮秒测量平台的光路呈现立体空间分布。不同于以往的高功率大型激光装置中的准直，马达反射镜的水平和俯仰转动导致近远场CCD上激光光斑的斜向移动而非传统的正交移动。提出了4×4维线性矩阵的准直算法，替代了以前的迭代逼近算法。经过实验验证，该模型能够实现近场准直精度小于0.16mm，远场调整精度小于0.17mrad，满足信噪比测量对准直精度的要求；并且，马达调整3次以下，准直时间2min以内，满足信噪比测量对准直时间的要求。拍瓦实验时，新型的信噪比测量仪的信号获取成功率由10%提升到90%，保证了信噪比实验结果满足总体的要求（大于106）。 第二，设计了带有衰减功能的双通道缩束单元，准直单元中的近远场CCD提供了离线可行性分析和在线监视的功能，保证了大能量和小能量通道输出到皮秒测量平台的激光光轴的同轴精度满足总体要求。 近场CCD和远场CCD主要用于监测大小能量通道切换时的激光光斑落点位置。在拍瓦实验之前，通过离线的测试和分析，证明了双通道设计的可行性，满足皮秒测量平台的使用要求。拍瓦实验时，合理使用大小能量通道，同时准直单元提供了实时监测，保证了双通道切换的准确性和高效性，实现了拍瓦激光脉冲各项参数的诊断和分析。 第三，设计了高效高精度的脉宽图像处理算法，实现了脉宽的在线实时测量。 在现有的脉宽测量分析软件基础平台上，利用C++语言编程设计了点最大、行最大、块最大和线积分的图像处理算法，以满足具有不同特征的脉宽图像的测量需求。通过软件编程，实现了对单峰脉宽图像和双峰脉宽图像的在线实时脉宽测量的功能。 |
| 英文摘要 | The high power laser facility includes a lot of subsystems and elements, and is for the study of the Inertial Confinement Fusion (ICF).The system of auto-alignment is a key subsystem and indispensable, it can guarantee that the laser facility runs efficiently. Picosecond measurement platform is used to measure and analyze several parameters [e.g., energy, pulse width, far-field (FF), and contrast] of petawatt laser compressed pulses. Unfortunately, measurement of the contrast of single-shot petawatt laser remains a difficult endeavor. The single-shot high-dynamic-range contrast measurement is also a world technique problem. The new single-pulse contrast measuring instrument has the difficult problem of online precision optical path debugging. In order to solve the problem, the paper describes the first application of auto-alignment in picosecond measurement platform. The beam shrunken unit with two channels and attenuation function is designed. The feasibility is proved by the near-field and far-field CCDs in the alignment system, achieving the automatic switch of the large and small energy. Besides, in order to improve the precision and efficiency of the pulse width measurement, image processing technology and software programming make the function of real-time measurement of the pulse width come true. The specific content includes the following several aspects: First, the alignment algorithm of a 4D linear matrix mathematical model in stereoscopic space is proposed. Measurement platform must exhibit a stereoscopic space distribution in diagnostic systems for petawatt laser to meet the requirement of a periodically poled lithium niobate (PPLN) crystal for light polarization in the new single-pulse contrast measuring instrument. For the laser beam in the stereoscopic space, horizontal and pitching rotation of motor reflectors results in the slope shift of laser spots in near-field and far-field CCDs, not the orthogonal shift of the traditional alignment in high power laser facility. The alignment algorithm of a 4D linear matrix replaces the traditional iterative algorithm. In the petawatt experiments, the alignment algorithm ensure that the near-field and far-field accuracy are less than 0.16 mm and 0.17 mrad respectively, meeting measurement requirement for alignment accuracy; the motors are adjusted less than three times, and the corresponding elapsed time is in 2 min, meeting measurement requirement for alignment time. The pulse acquisition probability of the contrast measuring instrument reaches 90% from 10%, to guarantee that the experimental result of pulse contrast can meet the general requirement (more than106). Second, design the beam shrunken unit with two channels and attenuation function. The near-field and far-field CCDs provide the function of offline feasibility analysis and online monitoring; assuring the laser coaxial precision of the two channels in picosecond measurement platform can meet the general requirement. The near-field and far-field CCDs are used for monitoring the position of laser spots when the two channels are switched. Before petawatt experiments, the offline test prove that the two channels is reliable. The large energy channel and the small energy channel are switched properly in the petawatt experiments, and the alignment unit offers the function of real-time monitoring, ensuring the accuracy and efficiency of the switch, achieving the measure and analysis of several parameters of the petawatt laser pulses. Third, design the high efficient and accuracy processing algorithms of pulse width image in the picosecond measurement platform, realizing the online real-time measurement of the pulse width. On the basis of the existing measurement and analysis software platform of pulse width, design image processing algorithms of the maximum point, maximum line, maximum block and integration method using the C++ programming language. These algorithms are for pulse width images with different characteristics. Software programming makes the function of online real-time measurement of the unimodal and bimodal pulse width images come true. |
| 语种 | 中文 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/16901]  |
| 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 | 秦海棠. 基于皮秒测量平台的光路准直技术与脉宽图像处理算法[D]. 中国科学院上海光学精密机械研究所. 2015. |
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