考虑光学望远镜系统的设计和配备与镜面视宁度相关, 本文引入了标准化点源敏感性(PSSn)来改善传统评价手段的局限性, 以实现镜面视宁度的全频域内评价。介绍了镜面视宁度的概念以及各大口径望远镜对镜面视宁度的检测与评价方法, 同时指出了之前使用的评价指标与评价方法的缺点不足。基于30 m望远镜研究团队所提出的全频域评价指标——标准化点源敏感性(PSSn)提出了新的评价方法。分析了PSSn的特性, 并利用其良好的合成特性以及不同的曝光函数, 得到了不同曝光条件以及视宁条件下的PSSn表达式。最后, 利用在大口径波前上随机选取子孔径的方法, 模拟了冻结湍流假设下的镜面视宁情况, 并对其PSSn的变化进行了估计, 验证了本文方法的可行性。基于本文所提出的对于镜面视宁度的评价与分析, 系统工程师可以全面客观地评价大口径系统的镜面视宁度, 结合PSSn的优良合成特性建立合理的误差树, 有效提高匹配精度, 降低系统建造成本。

As the design and assembly of optical systems in an optical telescope with large aperture mirrors are related to the mirror seeing, this paper introduces the normalized point source sensitivity (PSSn) to improve the limitation of traditional evaluation method and to realize the evaluation of mirror seeing in all frequencies. The concepts of the mirror seeing and its detection and evaluation methods were introduced and the shortcomings of the traditional evaluation methods and evaluation factors were pointed out. The evaluation index PSSn proposed by the 30 m large aperture telescope research group was introduced the new evaluation method. The PSSn properties were analyzed, and the expressions of the PSSn in different exposure conditions and seeing conditions were obtained based on the multiplication property and exposure conditions of the PSSn. The calculation procedure was given by considering the shutter time, mirror figure and atmosphere turbulence. Finally, with the help of random selection of sub-aperture on a large aperture wavefront, the ‘frozen turbulence’ was used to generate the simulated seeing condition over the mirror surface. The evaluation procedure was verified by this simulation. Based on the evaluation and analysis method presented in this paper, the system engineers could evaluate the mirror seeing for the large aperture optical system more objectively, and could build the error budget tree more reasonably to decrease the cost of the optical system.