Ju Guohao, Yan Changxiang, Gu Zhiyuan, Ma Hongcai
Appl Opt. 2018 Feb 20;57(6):1399-1409. doi: 10.1364/AO.57.001399.
In unobscured off-axis astronomical telescopes with an offset pupil, the effects of axial misalignments are very different from those in on-axis ones. Specifically, a series of nonrotationally symmetric aberrations with characteristic field dependence will be induced by axial misalignments. This paper takes off-axis two-mirror astronomical telescopes as an example to discuss the field characteristics of several important nonrotationally symmetric aberrations (including astigmatism, coma, and trefoil aberration) induced by axial misalignments in off-axis astronomical telescopes. The expressions of these aberrations are derived under some approximations. The accuracy of the proposed expressions is demonstrated. The specific field characteristics of these aberrations are presented and explicated. It is shown that the effects of axial misalignments bear strong similarities to the effects of the lateral misalignments in the symmetry plane of the off-axis system. On the other hand, the inherent relationships between astigmatism and coma induced by axial misalignments are further revealed, which are different from those induced by lateral misalignments. This fact presents the possibility of separating the effects of axial misalignments and lateral misalignments. Most of this work can be extended to other off-axis astronomical telescopes with more freedom.
在具有偏心光瞳的无遮挡离轴天文望远镜中，轴向失准的影响与同轴望远镜中的影响有很大不同。具体而言，轴向失准会引发一系列具有特征性场依赖性的非旋转对称像差。本文以离轴双镜天文望远镜为例，探讨离轴天文望远镜中轴向失准所引发的几种重要非旋转对称像差（包括像散、彗差和三叶形像差）的场特性。这些像差的表达式在一些近似条件下推导得出。所提表达式的准确性得到了验证。给出并阐述了这些像差的具体场特性。结果表明，轴向失准的影响与离轴系统对称平面内横向失准的影响有很强的相似性。另一方面，进一步揭示了轴向失准所引发的像散和彗差之间的内在关系，这与横向失准所引发的关系不同。这一事实为区分轴向失准和横向失准的影响提供了可能性。这项工作的大部分内容可以更自由地扩展到其他离轴天文望远镜。
