液晶双折射滤光器的性能对太阳磁场观测的影响研究

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	液晶双折射滤光器的性能对太阳磁场观测的影响研究
其他题名	Research on the influence of the performance of liquid crystal birefringent filter for solar magnetic field observations
	王远方舟
学位类型	博士
导师	金振宇
	2023-07-01
学位授予单位	中国科学院大学
学位授予地点	北京
学位专业	天文技术与方法
关键词	液晶双折射滤光器磁像仪偏振光学模拟窄带可调谐滤光器太阳磁场测量
摘要	太阳的磁场活动会在较小的空间和时间尺度上体现，对太阳进行高分辨磁场观测可以研究等离子体、磁场和辐射之间的相互作用机制，构建太阳大气的物理模型。一种常用的磁场测量方式是对磁敏谱线进行偏振观测，窄带可调谐滤光器是获得太阳多波长高分辨偏振数据的有利仪器。地基磁场观测设备依靠快速采集数据来减小湍流的影响，液晶双折射滤光器可以让磁像仪实现快速调制。 NVST 正在开展高分辨磁像仪研制的工作，液晶双折射滤光器是磁像仪的关键部件。在利用液晶双折射滤光器进行速度场测量时，出现滤光器扫描的轮廓中心点在不同视场出现偏移，红蓝翼与理论轮廓不能完全重合的情况。滤光器在不同的工作光路中也表现出不一样的特性。这些不一致会为磁场测量引入噪声，影响测量精度。本文针对液晶 Lyot 型双折射滤光器性能对太阳磁场观测影响的问题，开展了三个方面的研究工作：分析了 NVST 液晶 Lyot 滤光器的稳定性和均匀性；研究了 Lyot 型双折射滤光器在不同工作光路中的性能；为 NVST 望远镜设计了基于液晶 Lyot 型双折射滤光器的磁像仪。这些工作为太阳望远镜选择滤光器的工作光路提供方案，并推进了 NVST 磁像仪的研制工作。从上述三个方面出发，本文主要开展以下工作： 1）测试了 NVST 磁像仪选用的液晶 Lyot 滤光器的稳定性和均匀性。对滤光器的在线测试数据、液晶波片的实验室测试结果进行了细致的分析。并研究了稳定性和均匀性对滤光器透过率曲线，光谱扫描曲线的影响。 2）利用双折射滤光器的视场效应分析模型和 Zernike 多项式，建立了具有不同非均匀性的双折射滤光器模型。分析了 Lyot 型双折射滤光器的误差来源，利用 Zernike 多项式模拟了位相差分布为 PV3.7∘ 、PV4.5∘、PV5.7∘、PV7.8∘ 和 PV12.5∘ 的滤光器。分析了具有不同非均匀性的双折射滤光器在不同工作光路中的性能。当整个滤光器的非均匀性能够控制在 PV6∘ 以内时，远心光路的中心波长偏移量、旁瓣水平都优于准直光路。对于滤光器的均匀性较差时，例如存在液晶波片响应不均等情况，非均匀性可能超过 PV6∘，此时需选择准直光路。模拟工作为如何选择滤光器的工作光路提供了有利的分析数据和方法。 3）分析了 NVST 设计磁像仪的技术难点，设计了基于 Lyot 型双折射滤光器的磁像仪。NVST 磁像仪的技术难点包括：折轴光路带来的时变偏振、望远镜姿态变化和风载带来的光轴偏移以及湍流的影响等问题。讨论了同步成像系统的光学特性，滤光器的工作光路等问题，设计了磁像仪的整体结构和工作时序。最后利用 ZEMAX 光学设计软件为磁像仪设计了光路，为推进 NVST 磁像仪的研制做出贡献。本文对液晶双折射滤光器的性能研究工作和相应的成果为 NVST 开展的高分辨观测、速度场测量及磁像仪研制工作提供了明确的依据，对未来大口径太阳望远镜的高分辨仪器研制提供参考。
其他摘要	The magnetic activity of the Sun is manifested on small spatial and temporal scales, and high-resolution magnetic field observations of the Sun allow the study of the inter action mechanisms between plasma, magnetic fields, and radiation, and the construction of physical models of the solar atmosphere. A common form of magnetic field measure ment is polarisation observations of magnetically sensitive spectral lines. Narrow-band tunable filters are a favorite instrument for obtaining high-resolution polarisation data at multiple wavelengths from the Sun. Ground-based magnetic field observation equip ment relies on fast data acquisition to reduce the effects of turbulence, and liquid crystal birefringence filters allow for fast modulation of the magnetometer.NVST is engaged in the development of a high-resolution magnetometer, of which the liquid crystal bire fringent filter is a key component. When using liquid crystal birefringent filters for velocity field measurements, it occurs that the contour centroid of the filter scan is shifted in different fields of view and that the red and blue wings do not coincide exactly with the theoretical contours. The filters also exhibit different characteristics in different operating light paths.These inconsistencies can introduce noise into the magnetic field measurement and affect the accuracy of the measurement. In this paper, three areas of research have been carried out to investigate the ef fect of Lyot-type liquid crystal birefringent filter performance on solar magnetic field observations: the performance of Lyot-type birefringent filters in different operating optical paths; a comparison of the effect of different profile characteristics of Lyot-type birefringent filters on the measured profile of polarisation spectra; and the design of a magnetometer based on Lyot-type birefringent filters for the NVST telescope. This work provides a solution for the selection of the mount of the filter for the solar telescope and advances the development of the NVST magnetometer. The dissertation consists of the following five parts of work: (1)The stability and uniformity of the liquid crystal Lyot filter selected for the NVST magnetometer was tested. The results of on-line tests of the filters and labora tory tests of the liquid crystal waveplates were analysed in detail. The effect of stabilityand uniformity on the transmittance curve and spectral scan curve of the filter is also investigated. (2) An analytical model of the field-of-view effect of birefringent filters and Zernike polynomials are used to model birefringent filters with different non-uniformities. The error sources of Lyot-type birefringent filters are analyzed, and filters with a dislocation distribution of PV3.7∘ 、PV4.5∘、PV5.7∘、PV7.8∘ and PV12.5∘ are modeled using Zernike polynomials.The performance of birefringent filters with different non-uniformities in different operating optical paths is analysed. When the non-uniformity of the entire filter can be controlled to within PV6∘ , the telecentric optical path has a better central wavelength shift and partials than the collimated optical path, but the half-width will spread by 2 × 10−4Å. For poorer uniformity of the filter, e.g. when there is an uneven response of the liquid crystal wavelength, the non-uniformity may exceed PV6∘ and the collimated optical path needs to be selected. The simulation work provides favourable analytical data and methods for how to select the operating optical path of the filter. (3) The technical difficulties of designing a magnetic image camera by NVST are analysed, and a magnetic image camera based on a Lyot-type birefringent filter is de signed. The technical difficulties of the NVST include the time-varying polarisation caused by the bending-axis optical path, the optical axis shift caused by the telescope attitude change and wind load, and the effect of turbulence. The optical characteristics of the synoptic imaging system, the operating optical path of the filter and other issues are discussed, and the overall structure and operating timing of the magnetometer are designed. Finally, ZEMAX was used to design the optical path for the magnetometer, contributing to the advancement of the NVST magnetometer. The work on the performance of liquid crystal birefringent filters and the cor responding results in this paper provide a clear basis for the development of high resolution observations, velocity field measurements and magnetometers carried out by the NVST, and provide a reference for the development of high-resolution instruments for future large-aperture solar telescopes.
学科领域	天文学
学科门类	理学 ; 理学::天文学
页数	0
语种	中文
文献类型	学位论文
条目标识符	http://ir.ynao.ac.cn/handle/114a53/26413
专题	天文技术实验室
作者单位	中国科学院云南天文台
第一作者单位	中国科学院云南天文台
推荐引用方式 GB/T 7714	王远方舟. 液晶双折射滤光器的性能对太阳磁场观测的影响研究[D]. 北京. 中国科学院大学,2023.

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