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一种地基太阳望远镜焦点探测方法

A Focus Detection Method for Ground-Based Solar Telescope

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摘要

太阳强热辐射导致太阳望远镜光机系统热形变,引发较明显的时变焦点位置漂移。离焦像差影响高分辨观测,降低观测图像的空间分辨率,因此需要探测并补偿望远镜的离焦像差。由于大气湍流的影响,一般的基于图像处理的焦点探测方法不能有效地运用于地基太阳望远镜。而天文望远镜常用的基于Shack-Hartman波前探测的方法,在观测太阳边缘和低对比度的太阳米粒结构时无法工作。因此,提出一种基于图像能谱分析的焦点探测方法,该方法以图像能谱比的低频分量平均值作为焦点探测评价函数,能够消除目标信息的影响和平滑大气湍流的影响。实验证明,该方法的探测精度和探测时间分辨率能满足地基太阳望远镜不同观测目标的高分辨观测的需要。

Abstract

Intense solar radiation leads to thermal deformation of the solar telescope opto-mechanical system, triggering obvious time-varying focus shifts. Defocus aberration has an adverse effect on high-resolution observation and reduces the image spatial resolution. Therefore, the defocus aberration is necessary to be detected and compensated. Considering the effects of atmospheric turbulence, the focus detection method based on general image processing can not be applied well on ground-based solar telescopes. The focus detecting method based on Shack-Hartman wavefront detection which commonly used in astronomical telescopes is invalid at observing the solar limb and the low contrast solar granulation. The focus detecting method based on image power spectrum analysis is provided. This method used the average value of the low-frequency components of the image spectrum ratio as the cost function for focus detection, which can effectively eliminate the impact of object structure and atmospheric turbulence. Experimental results show that the detecting accuracy and frequency of this method can meet the requirement of high-resolution observations for different objects on ground-based solar telescope.

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中图分类号:P111

DOI:10.3788/aos201737.0711003

所属栏目:成像系统

基金项目:国家自然科学基金(11573068,11273059)

收稿日期:2017-01-12

修改稿日期:2017-04-05

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作者单位    点击查看

方玉亮:中国科学院云南天文台, 云南 昆明 650216中国科学院大学, 北京 100049
柳光乾:中国科学院云南天文台, 云南 昆明 650216
金振宇:中国科学院云南天文台, 云南 昆明 650216
李鹏飞:中国科学院云南天文台, 云南 昆明 650216中国科学院大学, 北京 100049
刘 忠:中国科学院云南天文台, 云南 昆明 650216

联系人作者:方玉亮(fyul@ynao.ac.cn)

备注:方玉亮(1989-),男,博士研究生,主要从事天文技术与方法方面的研究。

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引用该论文

Fang Yuliang,Liu Guangqian,Jin Zhenyu,Li Pengfei,Liu Zhong. A Focus Detection Method for Ground-Based Solar Telescope[J]. Acta Optica Sinica, 2017, 37(7): 0711003

方玉亮,柳光乾,金振宇,李鹏飞,刘 忠. 一种地基太阳望远镜焦点探测方法[J]. 光学学报, 2017, 37(7): 0711003

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