首页|A New Method for Monitoring Scattered Stray Light of an Inner-occulted Coronagraph
A New Method for Monitoring Scattered Stray Light of an Inner-occulted Coronagraph
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The scattered stray light of a coronagraph is a type of stray light that is generated by the objective lens as its surface defects are irradiated by sunlight.The defects mainly include dust and blemishes on the lens surface,microroughness of the lens surface,and impurity and inhomogeneity of the glass.Unlike the other types of relatively stable defects introduced when the objective lens is being manufactured,the scattered stray light caused by dusts on the lens surface is difficult to quantify accurately due to the disorder and randomness of the dust accumulation.The contribution of this type of stray light to the overall stray light level is difficult to determine through simulations and experiments.This can result in continuous deterioration of the stray light level of a coronagraph and thus affect the observation capabilities of the instrument.To solve this issue,through analyzing the forming mechanism of scattered stray light and ghost image generated by the inner-occulted coronagraph,we propose a novel method to monitor the scattered stray light from dusts by utilizing different stray light correlation coefficients.In this method,we first simulate and measure the level of stray light from the ghost image of the objective lens,and then determine the flux ratio of scattered light and ghost image on the conjugate plane.Although the flux ratio varies with the accumulation of dusts on the lens surface,it remains constant on the image plane.Therefore,the level of dust scattering light on the image plane can be obtained by using this ratio together with the level of ghost image stray light.The accuracy of this method has been validated in a laboratory by applying the objective lens with numerous surface cleanliness levels.
Da-Yang Liu、Hong-Xin Zhang、Ming-Zhe Sun、Zheng-Hua Huang、Li-Dong Xia、Wei-Xin Liu、Hui Fu
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Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment,Institute of Space Sciences,Shandong University,Weihai 264209,China
Changchun Institute of Optics,Fine Mechanics and Physics,Chinese Academy of Sciences,Changchun 130033,China
国家重点研发计划国家自然科学基金国家自然科学基金国家自然科学基金Chinese Meridian Project
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