Multi-conjugate adaptive optics (MCAO) uses two or more deformable mirrors (DMs) at conjugate altitudes approximately matched to the atmospheric turbulence layers to increase the corrected field of view. An important unresolved problem for MCAO is determining the optimal sequence of the DMs. Theoretical considerations and numerical studies suggest that ordering the DMs from lowest to highest altitude reduces the effects of scintillation, whereas on-sky experiments report that the best performance is attained with the ground-layer DM placed last. Using analytical calculations and numerical experiments with Fresnel propagation of Kolmogorov turbulence, we demonstrate that the scintillation results from spatial frequencies higher than the spatial sampling of high-altitude DMs are able to correct. Hence, the effect of scintillation is not impacted by MCAO correction regardless of the sequence of the DMs. Using end-to-end numerical simulations, we find that the dynamic misregistration between the DMs and the wavefront sensors is minimized by placing the ground-layer DM last, leading to increased loop stability and lower wavefront errors. Contrary to conventional wisdom, we recommend that the DMs be sequenced from highest to lowest altitude.

中文翻译：

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多共轭自适应光学中的闪烁效应和变形镜的最佳排列顺序

多共轭自适应光学 (MCAO) 在与大气湍流层大致匹配的共轭高度上使用两个或多个可变形反射镜 (DM) 来增加校正视野。MCAO 的一个重要未解决问题是确定 DM 的最佳序列。理论考虑和数值研究表明，从最低到最高高度对 DM 进行排序会降低闪烁的影响，而空中实验报告说，最后放置地层 DM 可以获得最佳性能。使用 Kolmogorov 湍流菲涅耳传播的分析计算和数值实验，我们证明了空间频率的闪烁结果高于高空 DM 的空间采样能够纠正。因此，无论 DM 的顺序如何，闪烁的效果都不受 MCAO 校正的影响。使用端到端数值模拟，我们发现通过最后放置接地层 DM 可以最大限度地减少 DM 和波前传感器之间的动态配准不良，从而提高环路稳定性并降低波前误差。与传统观点相反，我们建议从最高到最低高度对 DM 进行排序。