基于快速调谐滤光器的太阳大气谱线成像观测方法研究

YNAO OpenIR > 天文技术实验室

	基于快速调谐滤光器的太阳大气谱线成像观测方法研究
其他题名	Study on the Observation Method of Solar Atmospheric Spectral Imaging Based on the Rapid Tuning Filter
	王希群
学位类型	博士
导师	金振宇 ; 柳光乾
	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	太阳谱线成像液晶双折射滤光器液晶相位延迟器地基太阳望远镜
摘要	太阳磁场及其变化是太阳爆发并导致灾害性空间天气的主要因素，高分辨率二维磁场是当今太阳物理研究不可缺少的数据。当前太阳磁场测量通常采用对磁敏谱线进行偏振测量方式实现，利用窄带滤光器及偏振分析器可获得太阳大气多波长偏振数据，且便于进行高分辨重建。复杂的大气湍流是地基大口径太阳望远镜进行高分辨观测时无法回避的问题，使用快速调谐滤光器对太阳大气谱线进行成像观测可以一程度上减小大气湍流的影响。液晶相位可变延迟器是一种电控双折射器件，使用该器件对双折射滤光器波长进行快速调节是一种有效方式。国内外均对基于液晶相位延迟器的窄带滤光器进行了研究。太阳光球磁敏谱线带宽极窄，因此需要滤光带宽在0.1Å左右。极窄的滤光带宽对多级液晶滤光器的设计、加工、装配、控制及定标提出了更严苛的要求。本文针对基于快速调谐滤光器的太阳大气谱线成像观测方法开展了研究工作，使用液晶相位可变延迟器实现了滤光器的快速调谐，并在 NVST 上进行实测应用。工作内容包括基于快速调谐滤光器的太阳磁场测量方法研究;多级液晶Lyot滤光器研制、定标及试观测;液晶相位可变延迟器的高精度定标等三个方面。这几个方面的研究为在大口径地基太阳望远镜上进行谱线成像观测提供了部分软硬件条件。本文的主要研究结果和创新如下：1、研制了FWHM为0.1Å的液晶Lyot滤光器。在Lyot型双折射滤光器的基础上，使用LCVR对各Lyot单元的透过带进行精确控制。文中对基于LCVR的Lyot滤光器进行仿真分析，并提出了多级液晶Lyot滤光器的波长定标方法，可实现多级滤光器的快速定标。完成了单级、两级及六级滤光器实验，实现了液晶滤光器的同步控制。并在光谱仪上对六级液晶滤光器中心波长进行对齐。针对光谱仪对滤光器透过带的展宽作用，通过仿真分析，结合不同狭缝宽度下的实测结果，证明该滤光器实际FWHM符合设计需求，为0.1024Å。控制滤光器透过带到不同波长位置，确定其最大定位误差为0.006Å。2、实现了多级液晶滤光器的同步控制，研制了多级液晶Lyot滤光器控制系统。分别在高分辨光谱仪及NVST的太阳光球窄带观测实验系统上实现了液晶Lyot滤光器高效精确控制。滤光器定标阶段与光谱仪探测器配合工作，实现高效波长调谐及光谱数据处理。滤光器试观测阶段通过时序控制，可稳定获得高质量太阳光强单色像。实现了多级液晶Lyot滤光器控制程序的封装，便于不同场景的使用。3、搭建了太阳光球窄带观测实验系统并进行太阳大气谱线成像观测。在NVST仪器平台搭建了用于验证同步重建、快速调谐Lyot滤光器、频率漂移校正等关键技术的实验系统，并进行多项实验。测试了液晶Lyot滤光器在不同光路下的光学性能，对相位差法进行波前探测进行了实验探索，实现了观测系统全视场频率漂移高精度测量，基于实验系统获得高质量太阳光球单色图像，并测量了视向速度场。测得的宁静区视向速度与同时刻HMI数据一致。4、研制了基于双旋转波片的Mueller矩阵椭偏仪并对LCVR进行精确测量。该系统可对LCVR驱动电压-相位延迟量进行高速、高精度定标。文中对测量系统的测量方案进行分析，并选用双旋转波片方式进行偏振调制。使用系统自定标方式对系统固有系统误差进行测量，并在样品测量过程中校准了这些误差影响。对用于波长调谐的LCVR进行实测，获得其相位延迟量的时间稳定性、空间均匀性及电控分辨率。实测结果表明，LCVR在24小时内延迟量变化小于0.2°；40*40通光孔径内延迟量均匀性PV值小于8.4°；电控分辨率为1mV，在2.5V及3.5V附近延迟量调节分辨率分别为0.177°和0.077°。此外，实测LCVR光学响应时间不大于40ms。5、提出了全视场系统频率漂移的在线测量方法。利用太阳大气谱线轮廓扫描，实现了观测视场范围内频率漂移的精细测量。不改变观测系统光路，利用观测谱线对全视场频率漂移进行测量，通过望远镜平场模式平滑观测目标的空间结构，使用高斯函数拟合方式测量每个视场处的频率漂移。基于该方法，在NVST仪器平台搭建实验光路并进行频率漂移实测，结果表明全视场的频率漂移测量误差小于0.13pm。系统频率漂移的静态误差接近二次曲面，与理论模型一致；在102”视场范围内，系统频率漂移静态误差幅度为1.6pm；多次测量频率漂移均值随地球自转变化，且与望远镜指向范围相关，需尽可能保证观测区域处于日面中心，减小太阳自转引入的误差。利用该方法对太阳光球观测系统频率漂移进行在线高精度测量，可用于校正太阳大气速度场及磁场测量过程中的光谱数据，提高其测量精度。
其他摘要	The solar magnetic field and its variations are the main factors of solar eruptions and lead to disaster space weather, and the high-resolution two-dimensional magnetic field is indispensable data for today's solar physics research. Current solar magnetic field measurements are usually achieved by polarization measurements of magnetically sensitive spectral lines, and multi-wavelength high-resolution polarization data of the solar atmosphere can be obtained using narrow-band filters and polarization analyzers. Complex atmospheric turbulence is a problem that cannot be avoided by ground-based large-aperture solar telescopes for high-resolution observations, and the use of rapidly tunable filters for imaging solar atmospheric spectral lines can reduce the effect of atmospheric turbulence to a certain extent. The liquid crystal phase variable retarder is an electronically controlled birefringent device, and the use of this device is an effective way to perform fast adjustment of the birefringent filter wavelength. Narrowband filters based on liquid crystal phase retarders have been studied both at domestic and abroad. The bandwidth of the magnetically sensitive spectral lines of the sun's sphere is extremely narrow, so the filtering bandwidth needs to be around 0.01 nm. The extremely narrow filtering bandwidth imposes more stringent requirements on the design, processing, assembly, control and calibration of multi-stage liquid crystal filters.In this paper, we investigate a rapid-tuning filter-based observation method for solar atmospheric spectrum imaging, and use a liquid crystal phase-variable retarder to achieve rapid filter tuning, and apply it to NVST for real measurements.The work includes the study of solar magnetic field measurement method based on rapid tuning filter; multi-stage liquid crystal Lyot filter development, calibration and trial observation; high precision calibration of liquid crystal phase variable retarder and other three aspects. These aspects of the research provide part of the hardware and software for solar photospheric magnetic field measurements on a large-aperture ground-based solar telescope. The main research results and innovations of this paper are as follows:1. A liquid crystal Lyot filter with FWHM of 0.1 Å is successfully developed. Based on the Lyot-type birefringence filter, the transmission band of each Lyot unit is precisely controlled by using LCVR. In this paper, we simulate and analyze the LCVR-based Lyot filter, and propose a wavelength calibration method for multi-stage liquid crystal Lyot filters, which can realize the fast calibration of multi-stage filters. The experiments of single-stage, two-stage and six-stage filters were completed, and the synchronous control of liquid crystal filters was realized. And the center wavelength of the six-stage liquid crystal filter is aligned on the spectrometer. The simulation analysis was done for the effect of spectrometer on the spreading of the filter transmitting band, and the actual FWHM of the filter was proved to be 0.1024Å by different slit measurements, and the maximum positioning error was 0.006Å by controlling the transmitting band of the filter at different wavelength positions.2. Achieved synchronous control of multi-stage liquid crystal filters and developed a multi-stage liquid crystal Lyot filter control system. The liquid crystal Lyot filter was efficiently and precisely controlled on the high-resolution spectrometer and the NVST's solar photosphere narrow-band observation experimental system, respectively. The filter calibration stage works with the spectrometer detector to achieve efficient wavelength tuning and spectral data processing. The filter trial observation stage can obtain high quality solar intensity monochromatic image stably by timing control. The multi-stage liquid crystal Lyot filter control code package is realized to facilitate the use of other scenarios.3. A solar photospheric narrow-band observation experiment system was built and solar atmospheric spectral line imaging observations were performed. The experimental system for verifying key technologies such as synchronous reconstruction, fast tuning Lyot filter, and frequency drift correction was built on the NVST instrument platform, and several experiments were conducted. The optical performance of the liquid crystal Lyot filter under different optical paths was tested, the phase diversity method for wavefront detection was experimentally explored, the high-precision measurement of the frequency drift of the full field of view of the observation system was achieved, high-quality monochromatic images of the solar photosphere were obtained based on the experimental system, and the Doppler velocity field was measured. The measured Doppler velocity in the quiet region is consistent with the HMI data at the same moment.4. A Mueller matrix ellipsometer based on a dual rotating waveplate was developed and used for accurate measurements of LCVR. This system can perform high-speed and high-precision calibration of the LCVR driving voltage-phase retardance. The measurement scheme of the measurement system is analyzed in the paper, and the dual-rotating waveplate approach is selected for polarization modulation. The inherent systematic errors of the system are measured using the system self-calibration method, and the effects of these errors are calibrated during the sample measurement. The LCVR used for wavelength tuning was measured in real time to obtain the time stability, spatial uniformity and electrical resolution of its phase delay quantity. The measured results show that the delay variation of LCVR is less than 0.2° in 24 hours; the PV value of delay uniformity is less than 8.4° in the 40*40 through-aperture; the electric control resolution is 1mV, and the delay adjustment resolutions are 0.177° and 0.077° near 2.5V and 3.5V, respectively. In addition, the measured LCVR optical response time is not more than 40ms.5. An online measurement method for frequency drift of full-field-of-view systems is proposed. The fine measurement of wavelength drift within the observation field of view is achieved by using the solar atmospheric spectral line profile scan. Without changing the optical path of the observation system, the wavelength drift of the full field of view is measured using the observation spectral lines, and the spatial structure of the observation target is smoothed by the telescope flat field mode, and the frequency drift at each field of view is measured using a Gaussian function fitting method. Based on this method, the experimental optical path is built and the wavelength drift is measured on the NVST instrument platform, and the results show that the measurement error of the frequency drift is less than 0.13 pm. The static error of the system frequency drift is close to the quadratic surface, which is consistent with the theoretical model. The mean value of wavelength drift varies with the rotation of the Earth and is related to the pointing range of the telescope, so it is necessary to ensure that the observation area is at the center of the sun as much as possible to reduce the error introduced by the solar rotation. This method is used to measure the wavelength drift of the solar photosphere observation system online with high accuracy and can be used to correct the spectral data during the measurement of the solar atmospheric velocity and magnetic fields and improve their measurement accuracy.
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/114a53/26410
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	王希群. 基于快速调谐滤光器的太阳大气谱线成像观测方法研究[D]. 北京. 中国科学院大学,2023.

条目包含的文件
文件名称/大小	文献类型	版本类型	开放类型	使用许可
基于快速调谐滤光器的太阳大气谱线成像观测（16967KB）	学位论文		开放获取	CC BY-NC-SA	浏览请求全文