Determination and Experimental Study of Three Kinds of Stray Light in the Coronagraph System

doi:10.3788/gzxb20235211.1122003

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	Determination and Experimental Study of Three Kinds of Stray Light in the Coronagraph System
	Y. Huang; H. Zhang; Y. Ding and T. Wang
	2023
发表期刊	Guangzi Xuebao/Acta Photonica Sinica
ISSN	10044213
卷号	52 期号:11
摘要	The coronagraph is a scientific instrument developed to observe extremely faint coronal emission in the strong background of the solar disk. During the coronagraph observation and laboratory detection procedures，numerous non-imaging beams are present. The entrance of non-imaging beams into the detector has an adverse impact on the imaging contrast and these beams reaching the image plane are usually called stray light. In order to discern the subtle coronal signal，it is imperative for the coronagraph to effectively mitigate most forms of stray light present within the system. Due to the stark contrast in brightness between the corona and the solar photosphere，very strict requirements must be met in terms of the suppression of stray light to obtain reliable measurements. This paper primarily examines three forms of stray light within inner mask coronagraph systems as per the stipulations set forth by the requirements of the coronagraph，including the ghost images produced by the reflections from two surfaces of the objective，the scattering points from the objective，and the diffracted light from the aperture stop. The origins of the aforementioned three types of stray light can be attributed to the inherent characteristics of the solar corona system，and they can not be completely eliminated from the coronagraph itself. Therefore，alternative procedures must be implemented to effectively nullify the stray light prior to reaching the image plane. We simulate the coronagraph system using optical modeling software and plot the stray light propagation path within the optical system. Our analysis reveals that the propagation of the aforementioned three types of stray light in the optical system converges at multiple locations. Further，based on the corresponding propagation paths，we have established the respective intensity distribution patterns of the three types of stray light at their imaging location and the characteristics of these kinds of stray light are also analyzed. Upon conducting an in-depth analysis，it is discovered that the imaging locations of the three stray light types are in close proximity to each other，and exhibit similar imaging characteristics，resulting in significant interference to the detection process and the detection result of the system. Based on the simulation results，we summed up the causes of these stray lights and give the methods for detecting and mitigating these stray lights. At the same time，the corresponding experimental verification method is designed and a coronagraph with a field-of-view of ±1.08 R☉ ~2.5 R☉（R☉ represents the radius of the sun），a working wavelength range of 530.3~637.4 nm，and a total length of 3 713.28 mm was used for experimental comparison，and feasibility of the methods is verified. The camera used for the final image plane in this study was the Dhyana 95 V2 back-illuminated sCMOS camera. It boasted an effective pixel count of 2 048×2 048，an effective imaging area of 22.5 mm×22.5 mm，and a pixel size of 11 μm× 11 μm. The experimental results provide confirmation of the viability and efficacy of the aforementioned determination method. Moreover，the shelter and ghost image shielding structure is designed to mitigate the effects of stray light. The level of stray light was measured following the suppression，and it was found to meet the observation criteria. The stray light analysis and suppression implemented in this study broaden the array of available methods for mitigating stray light in coronal instrument systems，enhancing the efficiency and precision of laboratory-based detection of the coronagraph systems. © 2023 Chinese Optical Society. All rights reserved.
DOI	10.3788/gzxb20235211.1122003
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收录类别	ei
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文献类型	期刊论文
条目标识符	http://ir.ciomp.ac.cn/handle/181722/67541
专题	中国科学院长春光学精密机械与物理研究所
推荐引用方式 GB/T 7714	Y. Huang,H. Zhang,Y. Ding and T. Wang. Determination and Experimental Study of Three Kinds of Stray Light in the Coronagraph System[J]. Guangzi Xuebao/Acta Photonica Sinica,2023,52(11).
APA	Y. Huang,H. Zhang,&Y. Ding and T. Wang.(2023).Determination and Experimental Study of Three Kinds of Stray Light in the Coronagraph System.Guangzi Xuebao/Acta Photonica Sinica,52(11).
MLA	Y. Huang,et al."Determination and Experimental Study of Three Kinds of Stray Light in the Coronagraph System".Guangzi Xuebao/Acta Photonica Sinica 52.11(2023).

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