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光学系统的杂散光通常由衍射杂散光和散射杂散光共同构成,其中衍射杂散光是系统固有的不可消除的杂散光,是系统杂光设计的极限。衍射杂散光主要由光学系统口径、F数、工作波长、系统透过率和杂散光入射角等因素决定。衍射杂散光点源透射比计算公式为:
$${\rm PS{T_d}} = \frac{{\tau \lambda \cos \theta }}{{4D{\pi ^2}{F^2}{{\sin }^3}\theta }}$$ (1) 式中:D为入瞳口径;F为光学系统的F数;θ为杂散光离轴角;λ为中心波长;τ为透过率。图12为该系统衍射PST的分析结果。
系统在不同离轴角下的杂散光抑制能力如表1所示,系统总的杂散光分析结果如图13所示,仿真结果表明光学系统在观察5等星时,杂散光抑制能力满足观星要求。
表 1 系统不同离轴角PST
Table 1. Different off-axis angle PST of the system
Off-axis angle/(°) Diffraction PST Scattered PST Total PST 25 8.86E-07 5.58E-07 1.44E-06 30 5.11E-07 4.28E-07 9.39E-07 35 3.20E-07 9.90E-08 4.19E-07 40 2.13E-07 8.75E-08 3.00E-07 45 1.48E-07 6.85E-08 2.16E-07 50 1.06E-07 5.72E-08 1.63E-07 55 7.70E-08 4.61E-08 1.23E-07 60 5.68E-08 3.69E-08 9.37E-08 65 4.19E-08 2.14E-08 6.33E-08 70 3.04E-08 1.65E-08 4.69E-08 75 2.12E-08 8.25E-09 2.95E-08 80 1.34E-08 5.90E-09 1.93E-08
Optical system design of star sensor and stray light suppression technology
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摘要: 在星敏感器实际应用中,光学系统杂散光的存在会引起星点模糊或者被遮挡。文中根据星敏感器对口径、视场、光谱范围和探测能力的要求,采用Code V软件完成了星敏感器光学系统的设计,最终设计参数为口径15 mm、视场18°、光谱范围400~750 nm、探测能力5等星,并利用CAD画图软件设计了锥形结构遮光罩,遮光罩叶片视场边界为19°,共9片挡光环,最前端面距离窗口玻璃190.76 mm,最前端面口径108.76 mm,太阳规避角25°,同时利用ASAP软件分析了光学系统对杂散光的抑制能力,根据杂散光评价指标点源透射比(PST),在25°太阳规避角时,系统满足5等星探测能力需求,验证了杂散光分析方法、分析模型的正确性。Abstract: In the practical application of star sensors, the presence of stray light in the optical system will cause the star points to be blurred or blocked. Based on the requirements of the star sensor for aperture, field of view, spectral range and detection capability, the optical system design of star sensor was completed using Code V software. The final design parameters were 15 mm diameter, 18 degrees field of view, spectral range from 400 nm to 750 nm, detection capability 5 grade stars. A cone structure hood was designed with CAD drawing software, shading field of view boundary of the hood blade was 19°, and there were 9 light blocking rings in total. The front end face was 190.76 mm from the window glass, the front end face diameter was 108.76 mm, and the sun avoidance angle was 25°. At the same time, the ASAP software was used to analyze the optical system's ability to suppress stray light. According to the stray light evaluation index point source transmittance(PST), the system satisfies the detection capability requirements of 5th magnitude stars at a solar avoidance angle of 25°, which verifies the stray light analysis the correctness of methods and analytical models.
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Key words:
- optical system of star sensor /
- hood /
- point source transmittance(PST) /
- stray light
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表 1 系统不同离轴角PST
Table 1. Different off-axis angle PST of the system
Off-axis angle/(°) Diffraction PST Scattered PST Total PST 25 8.86E-07 5.58E-07 1.44E-06 30 5.11E-07 4.28E-07 9.39E-07 35 3.20E-07 9.90E-08 4.19E-07 40 2.13E-07 8.75E-08 3.00E-07 45 1.48E-07 6.85E-08 2.16E-07 50 1.06E-07 5.72E-08 1.63E-07 55 7.70E-08 4.61E-08 1.23E-07 60 5.68E-08 3.69E-08 9.37E-08 65 4.19E-08 2.14E-08 6.33E-08 70 3.04E-08 1.65E-08 4.69E-08 75 2.12E-08 8.25E-09 2.95E-08 80 1.34E-08 5.90E-09 1.93E-08 -
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