光纤阵列太阳光学望远镜研究组知识库

三维成谱成像技术是一种能够对观测视场中的所有展源目标进行实时光谱获取的技术，它可以通过单次采样同时获得目标光谱域和二维空间域信息。光纤积分视场单元（IFU）则是天文三维成谱成像技术的关键器件，通过将接收的像面切分，将像面信息细分到若干单元传递至光谱仪，在此过程中二维的展源目标被重整为互不干扰的线性排列供光谱仪进行采样提取，能有效提高天文观测的时间分辨率。介绍一种具有242光纤单元的IFU,该IFU目前应用于中科院云南天文台的光纤阵列太阳光学望远镜（型号FASOT-1B）系统。为满足FASOT-1B的指标要求，获得高传输效率、高光谱分辨率和高时间分辨率观测效果，该IFU采用微透镜阵列加光纤阵列的结构，该微透镜为正六边形球面镜，实现接近100%的空间填充率。综合考虑光纤积分视场单元前置望远镜系统和后端光谱仪系统的设计参数，优化设计了一对11×11的微透镜阵列，相邻微透镜间距300μm,每个微透镜对应天区1.5″,以焦比F/8.2将接收到的光汇入与其对应的光纤纤芯中。系统分析光纤芯径与光谱仪光谱分辨率间的关系，设计的光纤规格为：35/105/125μm,该设计既能满足光纤接收微透镜所传递的全部光信息，同样可以得到系统需求的光谱分辨率和相对短的狭缝宽度。量化分析IFU阵列端光纤直径与微微孔深度对光纤实际入射焦比的影响，选定的微孔尺寸直径130μm,深3 mm。阵列端二维排布的光纤在赝狭缝端经过重整，以线性排列将光信息导入光谱仪，相邻光纤间距130μm。整个IFU的能量传输效率均值77.7%,波动值RMS 1.6%;所有光纤出射焦比EE90均慢于F/7。IFU出射端（赝狭缝端）光纤横向（排列方向）偏移量RMS值小于2.7μm,纵向（垂直于排列方向）偏移量RMS值小于1.8μm。FASOT-1B系统安装IFU并调试后进行了验证性观测，成功获取了太阳NOAA12738活动区MgI色球的斯托克斯光谱，该IFU也成为国内首个自主研制并应用于科学观测的光纤加微透镜型IFU。 

Astronomical three-dimensional spectral imaging technology is a real-time spectral acquisition technology for all source targets in the observation field of view. It can simultaneously obtain the spectral domain and two-dimensional spatial domain information of the target by single sampling. Optical fiber integral field unit(IFU)is the key component of astronomical threedimensional spectral imaging technology. The image plane information is subdivided into several units and transmitted to the spectrometer through the segmentation of the received image plane. In this process, the two-dimensional spread source target is reorganized into a non-interference linear array for sampling and extraction by the spectrometer, which can effectively improve the temporal resolution of astronomical observation. This paper introduces an IFU with 242fiber units, currently applied to the fiber array solar optical telescope(FASOT-1B)system of Yunnan Observatory of the Chinese Academy of Sciences. In order to meet the index requirements of FASOT-1Band obtain the observation effect of high transmission efficiency, high spectral resolution and high time resolution, the IFU adopts the structure of a microlens array and fiber array. The microlens is a regular hexagon spherical mirror, and the spatial filling rate is nearly 100％. Considering the design parameters of the front telescope system and the back-end spectrometer system of the fiber integral field-of-view unit, apair of 11×11microlens arrays is an optimized design. The distance between adjacent microlens is 300μm, and each microlens corresponds to the sky area of 1. 5″. The received light is incorporated into the corresponding fiber core with the focal ratio F/8. 2. The relationship between fiber core diameter and spectral resolution of the spectrometer is analyzed systematically. The design specifications of the fiber are 35/ 105/125μm. This parameter can not only meet the requirements of the optical fiber to receive all the optical information transmitted by the microlens but also can obtain the spectral resolution and relatively short slit width to meet the system’s requirements. The influence of fiber diameter and micro-hole depth on the actual incidence focal ratio of the IFU array is quantitatively analyzed, and the micro-hole size is selected as 130μm in diameter and 3mm in depth. A two-dimensional arrayed optical fiber is reorganized at the pseudoslit end, and the optical information is imported into the spectrometer in a linear arrangement. The distance between adjacent fibers is 130μm. The problem of IFU fiber fixation and polishing is solved. The average energy transmission efficiency of IFU is 77. 7％, and the RMS is 1. 6％. All fiber output focal ratio EE90is slower than F/7. The RMS value of the lateral(alignment)offset of the IFU pseudo-slit end fiber is less than 2. 7μm, and the RMS value of the longitudinal(perpendicular to alignment)offset is less than 1. 8μm. After the installation and debugging of IFU and FASOT-1Bsystems, the confirmatory observation was carried out, and the Stokes spectrum of the MgI chromosphere in the solar NOAA12738active region was successfully obtained. This IFU has also become the first fiber plus convex lens IFU independently developed and applied to scientific observation in China.