白光日冕仪光学系统的杂散光抑制

摘要

To meet the demands on suppressing strictly stray light for a coronagraph,a white corona-graph is designed based on its working principle and the properties of stray light.The white corona-graph shows its main specifications in the field of view of 2.5 R_⊙ to 15 R_⊙,a resolution of 14",a aperture of 30 mm,a focal length of 200 mm,and the total length of 1080 mm.Furthermore,the length of optical structure is 370 mm and the MTF value at 37 pl/mm is above 0.5.The four kinds of stray light sources is analyzed in detail,which is direct sun light,the diffractive light of sun light at edge of an external occulter D_1,the diffractive light of sun light at edge of a field stop A_1,and the multi-reflection light in the objective O_1.With the help of conjugated stops,a stray light suppressing structure is designed.Experiment results show that four main stray light sources are totally suppressed and the stray light suppressing level reaches 10~(-8) -10~(-10) B_⊙,which satisfies the system requirements.%为满足日冕仪对杂散光抑制的苛刻要求,通过分析日冕仪的工作原理和结构特点,设计了白光日冕仪光学系统,系统观测范围为2.5～15 R_⊙,角分辨率为14″,口径为30 mm,焦距为200 mm,系统总长为1 080 mm;其中光学系统长370 mm,37 pl/mm的MTF值＞0.5.分析了直射太阳光、太阳光在外掩体D1边缘的衍射光、视场光阑A1边缘的衍射光、以及物镜组O_1各表面多次反射带来的系统杂散光的特点,利用多个光阑互相共轭的空间位置关系,设计了相应的杂散光抑制结构,从而完全抑制了系统的4个主要杂散光光源产生的杂散光,使系统整体杂散光抑制水平达到10~(-8)～10~(-10) B_⊙,满足了日冕仪光学系统对杂散光抑制的要求.