Suppresion of stray light ghost image in internally occulting refractive ground-based coronagraph
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摘要:为了消除杂散光对日冕仪成像质量的影响,分析了工作波段为530~555 nm的内掩式透射地基日冕仪(其视场为1.1~3R⊙,分辨率为13.5 m,口径为120 mm,系统F数为8.2)物镜的多次反射形成的鬼像。基于鬼像形成原理,完成建模模拟,提出了结构性遮拦措施,并通过实验论证了遮拦结构对鬼像有良好的遮拦效果,同时验证了鬼像的光强和物镜边缘衍射光基本一致。实验还显示:鬼像的尺寸和模拟基本一致,直径均约为0.9 mm。消除鬼像后,内掩式透射日冕仪消杂光能力和成像质量进一步提高,实现了对日冕的有效观测。
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关键词:
- 内掩式透射地基日冕仪/
- 鬼像/
- 杂散光/
- 结构遮拦
Abstract:In order to improve the imaging quality of coronagraphs, the ghost image caused by multi-reflection light from an objective lens for the internally occulting refractive ground-based coronagraph is analyzed at a band from 530 nm to 555 nm. The coronagraph with an aperture of 120 nm shows its main specifications in a field of view of 1.1 to 3R⊙, a resolution of 13.5 m, and F number of 8.2. The paper analyzes its imaging theory and establishes a model for the ghost image. Then, it presents the structure masking measures and performs an experimental demonstration. The experiment result shows that the masking structure is effective on the elimination of ghost image. In addition, the intensity of ghost image and the intensity of diffracted light of objective lens edge are basically the same. The experiment also illuminates that the size of ghost image is the same as the simulation result of 0.9 mm.The ghost image suppressing further improves the capability of elimination of stray light and the image quality of the coronagraph achieves the effective observation of the solar corona. -
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