大型太阳望远镜镜面视宁度的实验研究  

Experiment study on large solar telescope mirror seeing

作　　者：王焱[1,2] 杨永兴 李金鹏 毕勇[1,2,3] 朱庆生 Wang Yan;Yang Yongxing;Li Jinpeng;Bi Yong;Zhu Qingsheng(Nanjing Research Center of Astronomical Instruments,Chinese Academy of Sciences,Nanjing 210042,China;University of Science and Technology of China,Hefei 230022,China;Nanjing Astronomical Instruments Co.,Ltd.,Chinese Academy of Sciences,Nanjing 210042,China)

机构地区：[1]中国科学院南京天文仪器研制中心,江苏南京210042 [2]中国科学技术大学,安徽合肥230022 [3]中科院南京天文仪器有限公司,江苏南京210042

出　　处：《红外与激光工程》2024年第1期225-235,共11页Infrared and Laser Engineering

基　　金：江苏省自然科学基金项目(BK2023022139)。

摘　　要：太阳望远镜内部因太阳辐射作用使镜面升温,镜面上方产生局部大气湍流,导致镜面视宁度不佳,从而造成像质的严重衰减。文中基于温度梯度和气体流动导致固体-流场的耦合作用,提出镜面视宁度效应的形成机制,建立湍流大气光学产生镜面视宁度效应的理论,利用1 550 mm大口径双曲面镜的实验数据推导并验证镜面视宁度的实验模型,并对太阳望远镜主镜温控目标进行确定。在自然对流和强迫对流两种条件下,不同环境风速时镜面温差改变对镜面视宁度的影响。结果表明:镜面温差和环境风速与镜面视宁度相关性很强,增加主动通风可以降低镜面视宁度。温差是4℃条件下,自然对流时镜面视宁度为1.43″;温差是3℃条件下,0.2 m/s强迫对流时镜面视宁度为0.44″,1 m/s强迫对流时镜面视宁度为0.27″。根据镜面视宁度效应容差标准,在0.2 m/s强迫对流条件下,镜面-空气温差应控制在0.2 K以下;在1.0 m/s强迫对流条件下,镜面-空气温差应控制在1 K以下。此研究成果旨在揭示空气湍流的形成机理与传播规律及其对望远镜像质退化影响规律,为提升大口径太阳望远镜工作分辨率奠定基础。Objective The primary mirrors of large solar telescopes are continuously affected by solar radiation,causing the mirror surface temperature to be higher than the air temperature.Under the action of the temperature difference between the mirror surfaces,the air near the mirror surface is heated,causing the air density to be unevenly divided,resulting in abnormal atmospheric refraction,resulting in mirror seeing,which degrades the image quality of the solar telescope.Solar telescopes mostly use Gregorian optical systems,and their primary mirrors are aspherical mirrors.Foreign experimental research mainly uses plane mirrors or spherical mirrors for experiments.However,due to factors such as mirror surface shape,effective aperture and experimental optical path,the theoretical relevance of the experimental results is low.Mirror seeing is the coupling effect between the mirror and the surrounding air.Only numerical simulations have been carried out in China,and no relevant experimental research has been conducted on mirror seeing.Direct experimental detection is a more reliable solution.In order to control the near-mirror seeing caused by the temperature increase of the primary mirror,the mirror temperature control target needs to be given quantitatively.The main mirrors of large-aperture solar telescopes mostly use aspherical mirrors.The experimental platform of this article uses a 1550 mm diameter hyperbolic mirror for research to improve the universality of the experimental results.Methods First,based on the solid-flow field coupling caused by temperature gradient and gas flow,this paper proposes the formation mechanism of the specular seeing effect and establishes the theory of the specular seeing effect caused by atmospheric optical turbulence.Then,based on the physical process of atmospheric turbulence producing mirror seeing,under two conditions of natural convection and forced convection(Fig.1),an experiment for a 1550 mm large-diameter hyperbolic mirror was built(Fig.3),and the experimental data(Tab.2-4),analy

关 键 词：大气光学 镜面视宁度 大气湍流 太阳望远镜 弗劳德数 

分 类 号：O435.1[机械工程—光学工程] TP391.4[理学—光学]