Low-Order Aberrations in Band-limited Lyot Coronagraphs
Low-Order Aberrations in Band-limited Lyot Coronagraphs
复制标题
带限 Lyot 日冕仪中的低阶像差
DOI：
10.1086/466507
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发表时间：
2005
期刊：
影响因子：
--
通讯作者：
R. Makidon
中科院分区：
文献类型：
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作者：
A. Sivaramakrishnan;R. Soummer;Allic Sivaramakrishnan;J. Lloyd;B. Oppenheimer;R. Makidon
我们研究了Lyot日冕仪对小的、低阶相位像差的反应方式。本研究适用于工作在90%及更高斯特雷特比的地基自适应光学日冕仪，以及一些本质上具有更高斯特雷特比成像的天基日冕仪。我们利用单色点扩散函数的二阶展开式（写为光阑上相位像差的幂级数的功率谱）推导出“带限”Lyot日冕仪（BLC）对小的、低阶的相位像差响应的解析表达式。BLC具有一个带掩斑的焦平面掩模，其不透明度轮廓是空间带限制函数，而不是硬边缘的不透明圆盘。BLC在一阶上对倾斜和散光不敏感。在焦平面掩模之后的再成像瞳孔平面（Lyot平面）中减小孔径可以减轻像散的二阶效应，但代价是系统吞吐量和角分辨率。这种缩小尺寸的最佳程度取决于个别仪器的设计和目标。我们的分析工作产生了物理洞察力，并补充了关于这个主题的现有数值工作。我们的方法可以扩展到处理高阶像差通过带限制的Lyot日冕仪通过使用我们的多项式分解或类似的傅立叶方法。
We study the way Lyot coronagraphs with unapodized entrance pupils respond to small, low-order phase aberrations. This study is applicable to ground-based adaptive optics coronagraphs operating at 90% and higher Strehl ratios, as well as to some space-based coronagraphs with intrinsically higher Strehl ratio imaging. We utilize a second-order expansion of the monochromatic point-spread function (written as a power spectrum of a power series in the phase aberration over clear aperture) to derive analytical expressions for the response of a "band-limited" Lyot coronagraph (BLC) to small, low-order, phase aberrations. The BLC possesses a focal plane mask with an occulting spot whose opacity profile is a spatially band-limited function rather than a hard-edged, opaque disk. The BLC is, to first order, insensitive to tilt and astigmatism. Undersizing the stop in the reimaged pupil plane (the Lyot plane) following the focal plane mask can alleviate second-order effects of astigmatism, at the expense of system throughput and angular resolution. The optimal degree of such undersizing depends on individual instrument designs and goals. Our analytical work engenders physical insight and complements existing numerical work on this subject. Our methods can be extended to treat the passage of higher order aberrations through band-limited Lyot coronagraphs by using our polynomial decomposition or an analogous Fourier approach.