Bai Xiaoquan, Ju Guohao, Ma Hongcai, Xu Shuyan
Appl Opt. 2019 Oct 1;58(28):7693-7707. doi: 10.1364/AO.58.007693.
Due to the absence of rotational symmetry, the effects of axial and lateral misalignments couple tightly together, which leads to special aberration field characteristics. This paper will present an in-depth and systematic discussion on the interactions between the effects of axial and lateral misalignments in pupil-offset off-axis two-mirror astronomical telescopes. The aberration function of this class of telescopes in the presence of axial and lateral misalignments is derived. The specific expressions of two dominant non-rotationally symmetric aberrations, i.e., astigmatism and coma, are obtained and the aberration field characteristics are discussed. Importantly, it is shown that under certain conditions, a node will arise in the field of view for these two kinds of aberrations. Then the aberrational compensation mechanisms between axial and lateral misalignments are quantitatively explicated, and it is shown that the non-rotationally symmetric aberrations induced by axial misalignments can well be compensated by lateral misalignments. However, we also find that in this process, the defocus aberration induced by these two kinds of misalignments will accumulate (rather than cancel out). Therefore, in practice, it is better to separate these two kinds of misalignment. Finally, we propose a simple method to decouple axial misalignments from lateral misalignments with wavefront measurement at one field position. Most of this work can be extended to other kind of pupil-offset off-axis astronomical telescopes, such as off-axis three-mirror anastigmatic telescopes.
由于缺乏旋转对称性，轴向和横向失准的影响紧密耦合在一起，这导致了特殊的像差场特性。本文将对光瞳偏移离轴双镜天文望远镜中轴向和横向失准影响之间的相互作用进行深入系统的讨论。推导了这类望远镜在存在轴向和横向失准情况下的像差函数。得到了两种主要的非旋转对称像差（即像散和彗差）的具体表达式，并讨论了像差场特性。重要的是，结果表明在某些条件下，这两种像差在视场中会出现一个节点。然后定量地阐明了轴向和横向失准之间的像差补偿机制，结果表明轴向失准引起的非旋转对称像差可以通过横向失准得到很好的补偿。然而，我们也发现在此过程中，这两种失准引起的离焦像差会累积（而不是抵消）。因此，在实际中，最好将这两种失准分开。最后，我们提出了一种在一个视场位置通过波前测量将轴向失准与横向失准解耦的简单方法。这项工作的大部分内容可以推广到其他类型的光瞳偏移离轴天文望远镜，如离轴三镜消像散望远镜。
