大型太阳望远镜偏振测量系统的定标方法研究

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	大型太阳望远镜偏振测量系统的定标方法研究
其他题名	Research on Calibration Method of Polarimetry for Large Solar Telescope
	彭建国
学位类型	博士
导师	季凯帆 ; 袁沭
	2021-07-01
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	望远镜的偏振定标偏振测量 Mueller矩阵测量偏振光学模拟晶体元件干涉
摘要	太阳磁场在太阳活动和空间天气的研究中具有重要意义，而偏振测量是目前获得太阳磁场信息的主要手段。当前国内外主镜口径一米及以上的大太阳望远镜都在偏振测量方面有明确的要求，我国已经建成的NVST，正在研制的2mRST以及预研中的CGST也都专注于对太阳磁场的偏振观测。在太阳偏振观测中，需要采用偏振元件来对观测信号进行调制，偏振元件参数的定标是实现望远镜偏振测量的基础。对于大型太阳望远镜，常采用折轴光路将光引入库德房后再进行偏振观测，对望远镜系统的偏振定标和建模是克服望远镜偏振造成影响的重要手段。对于大型太阳望远镜的高精度偏振观测，晶体元件所处的光束特性以及元件中的光学干涉都会给偏振测量结果带来影响，对晶体元件入射角特性和干涉特性的模拟分析能为偏振观测提供重要的指导。本文针对大型太阳望远镜在偏振测量中面对的主要问题进行了研究，从偏振元件的实验室测量、望远镜系统的偏振建模以及晶体元件的偏振特性模拟等三方面开展研究工作。这三方面的工作为太阳望远镜偏振测量系统的定标提供了实验室的测量条件、模型定标方法和模拟仿真方案。本文从上述三方面出发，主要开展了以下五部分的研究工作：1、提出了基于双光束检偏的固定延迟波片的测量方法，该方法克服了偏振元件对准偏差对测量结果的影响，能够实现对波片延迟量和方位角的高精度测量。对该方法的系统状态和样品的测量范围进行了分析，并对测量系统的主要误差——探测器的非线性响应进行了校准。采用该测量方法对波片样品延迟量和方位角的测量精度为0.05°以上，为望远镜旋转波片型偏振分析器的调制和解调方案提供了实验室测量基础。2、基于双旋转波片Mueller矩阵测量系统的原理，发展了该原理中的角度旋转方案，得到本文中的测量系统。对该测量系统的测量方案和误差来源进行了分析，采用自定标的方法对仪器的主要误差进行了校准。采用校准后的测量系统，对实验室和NVST上的光学元件进行了Mueller矩阵测量和分析，发现了一些元件与理论设计之间的偏差，并给这些元件的使用提出了指导方案。该测量系统作为光学元件的测试平台，Mueller矩阵测量精度约为2×10-3，为望远镜进行偏振测量和偏振定标提供了实验室基础。3、提出了基于机器学习对望远镜进行偏振建模的方法，将该方法用在NVST的偏振建模上，克服了传统物理参数建模中模型参数不完善造成的偏差，提高了模型精度。该建模方法结合了物理参数建模与机器学习建模的优势，能够在保证模型稳定性的基础上提高精度。采用机器学习建模方法后，NVST偏振模型的精度由原先的0.04提高到了0.02。根据NVST目前进行偏振定标和偏振建模的结果，提出了下一步获得定标数据的方案。该工作对NVST偏振建模面对的问题进行了处理，为后续大型望远镜的偏振定标提供了方法指导。4、基于偏振光线追迹矩阵法，对NVST中偏振定标波片和偏振测量波片的入射角特性进行了模拟，并对入射角特性给偏振定标和偏振测量的影响进行了分析。根据模拟结果，入射角特性对不同视场下偏振测量的影响可以忽略。对于偏振定标，只需考虑定标波片在实际会聚光束下延迟量的偏离，不同视场下偏振定标的差异可以忽略。该模拟方法能够分析复杂入射角下晶体光学元件的偏振特性，为后续望远镜进行偏振测量系统的模拟提供了有效工具。5、基于薄膜干涉中的Berreman算法，模拟分析了干涉对NVST偏振定标波片和偏振测量波片特性的影响，并分析了该影响最终对NVST偏振定标和偏振测量造成的结果。根据模拟得到，偏振测量波片中沿波长方向的干涉条纹是影响偏振测量的主要因素，需要通过实测获得并改正。该模拟方法是分析望远镜中光学元件干涉特性的有用工具，为后续望远镜偏振测量系统的分析和定标提供了模拟手段。本文的研究工作和相应的成果实现了望远镜中相关光学元件的高精度测量、望远镜系统的偏振建模和晶体元件的模拟，为望远镜系统的偏振测量与偏振定标提供了保证。
其他摘要	The solar magnetic field is of great significance in the study of solar activity and space weather, and polarization measurement is currently the main method for obtaining solar magnetic field information. At present, large solar telescopes, with a primary mirror diameter of one meter or more, have clear requirements for polarization measurement. The NVST that has been built in my China, the 2mRST under development and the CGST in pre-research also focus on the polarization observation of the solar magnetic field. In the solar polarization observation, polarization elements are essential to modulate the observational signal, and the calibration of the parameters of the polarization elements is the basis for realizing the polarization measurement of the telescope. For large solar telescopes, a relay optics is often used to introduce light into the Coude room and then perform polarization observations. Polarization calibration and modeling of the telescope system are important means to overcome the effects of telescope polarization. For the high-precision polarization observation of large solar telescopes, the beam characteristics of the crystal element and the interference in the element will affect the polarization measurement results. The simulation analysis of the incident angle characteristics and interference characteristics of the crystal element can provide important guidance for polarization observations.The thesis studies the main problems faced by large solar telescopes in polarization measurement, from the following three aspects: laboratory measurement of polarization elements, polarization modeling of telescope systems, and simulation of crystal elements. The work of the three aspects provide laboratory measurement platform, calibration modeling method and polarization simulation for polarization measurement of the solar telescope.The dissertation consists of the following five parts of work:1. A measurement method of waveplate based on dual-beam polarization analyzer configuration was proposed. This method overcomes the influence of alignment deviation of polarization element on the measurement result, and can achieve high-precision measurement of the retardation and azimuth angle. The system configuration of the method and the measurement range of the sample were analyzed, and the main error of the measurement system, the nonlinear response of the detector, was calibrated. The measurement accuracy of the retardation and azimuth angle of the wave plate sample by this measurement method is higher than 0.05°, which provides a laboratory measurement platform for the modulation and demodulation scheme of rotating wave plate polarimeter.2. Based on the dual-rotating wave plate Mueller matrix measurement system, the rotation scheme of the system is proposed. The measurement plan and error sources of the system are analyzed, and the main errors of the system are calibrated by the method of self-calibration. Using the calibrated measurement system, the Mueller matrix measurement and analysis of the optical elements in the laboratory and NVST were carried out, and some deviations between the elements and the theoretical design were obtained, and guidelines were proposed for the use of these components. The measurement system is used as a test platform for optical components. The measurement accuracy of the Mueller matrix is about 2×10-3, which provides a laboratory basis for the polarization measurement and calibration of the telescope.3. A method for polarization modeling of telescopes based on machine learning is proposed. This method is used in the polarization modeling of NVST, which overcomes the deviation caused by imcompleteless of model parameters in traditional physical parametric model, and improves the accuracy of the model. This modeling method combines the advantages of physical parameter model and machine learning model, and can improve accuracy while ensuring model stability. After adopting the machine learning model, the accuracy of the NVST polarization model has been increased from 0.04 to 0.02. Based on the results of the polarization calibration and modeling currently carried out by NVST, the scheme for the next step calibration is proposed. This work deals with the problems faced by NVST polarization modeling, and provides guidance for subsequent polarization calibration of large telescopes.4. Based on the polarization ray tracing, the wave plates for the polarimeter and polarization calibration unit of NVST were analyzed, and the relationship between the polarization characteristics of the two wave plates and the incidence angle was obtained. Furthermore, the influence of the incident angle of the two wave plates on the NVST polarization calibration and measurement is further analyzed, and its influence can be ignored under the current polarization measurement accuracy. The simulation program is an effective tool for analyzing the polarization characteristics of birefringent optical elements, and provides a practical means for the simulation of the polarization measurement system of the next generation telescope.5. Based on the Berreman calculus in thin film interference field, the effect of interference on the wave plates of NVST are simulated and analyzed, and the impact on the NVST polarization calibration and polarization measurement is analyzed. According to the simulation, the interference fringes along the wavelength in the polarization measurement waveplate are the main factors affecting the polarization measurement, and need to be obtained and corrected through actual measurement. The simulation method is a useful tool for analyzing the interference characteristics of optical elements in the telescope, and provides a simulation method for the analysis and calibration of the telescope polarization measurement system.The research work in this paper and the corresponding results have realized the high-precision measurement of the relevant optical elements in the telescope, the polarization modeling of the telescope system and the simulation of the crystal element, which provide a guarantee for the polarization measurement and polarization calibration of the telescope system.
学科领域	天文学 ; 太阳与太阳系 ; 太阳与太阳系其他学科 ; 机械工程 ; 仪器仪表技术 ; 光学技术与仪器 ; 天文仪器
学科门类	理学 ; 理学::天文学 ; 工学 ; 工学::仪器科学与技术
页数	157
语种	中文
文献类型	学位论文
条目标识符	http://ir.ynao.ac.cn/handle/114a53/25505
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	彭建国. 大型太阳望远镜偏振测量系统的定标方法研究[D]. 北京. 中国科学院大学,2021.

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