标题： 大气图像模糊与有限外尺度或部分自适应校正 显示英文标题

标题： Atmospheric image blur with finite outer scale or partial adaptive correction

摘要： 在宽波长范围内工作的大型望远镜的视宁度限制分辨率主要取决于湍流外尺度，不能仅用一个“视宁度”值来充分描述。 我们试图澄清对此问题的常见混淆。 我们通过解析计算和数值模拟研究有限湍流外尺度和部分自适应校正的影响。 如果采用冯·卡门湍流模型，一个简单的近似公式可以捕捉大气长时间曝光分辨率在外尺度整个实际感兴趣的望远镜口径和波长范围内的依赖关系。 在红外（IR）波段，与标准科莫戈罗夫视宁度公式相比，差异可能超过两倍。 我们发现，低阶自适应湍流校正会产生有效小外尺度的残余波前，因此即使非常低的补偿阶数也能显著提高分辨率，相比标准理论有明显改善。 目前，大型望远镜的视宁度限制分辨率，尤其是在红外波段，由于未考虑外尺度而被低估。 另一方面，专为红外波段衍射极限成像设计的自适应光学系统，可以将可见光波段的分辨率提高多达两倍。 显示英文摘要

摘要： Seeing-limited resolution in large telescopes working over wide wavelength range depends substantially on the turbulence outer scale and cannot be adequately described by one "seeing" value. We attempt to clarify frequent confusions on this matter. We study the effects of finite turbulence outer scale and partial adaptive corrections by means of analytical calculations and numerical simulations. If a von Karman turbulence model is adopted, a simple approximate formula captures the dependence of atmospheric long-exposure resolution on the outer scale over the entire practically interesting range of telescope diameters and wavelengths. In the infrared (IR), the difference with the standard Kolmogorov seeing formula can exceed a factor of two. We find that low-order adaptive turbulence correction produces residual wave-fronts with effectively small outer scale, so even very low compensation order leads to a substantial improvement in resolution over seeing, compared to the standard theory. Seeing-limited resolution of large telescopes, especially in the IR, is currently under-estimated by not accounting for the outer scale. On the other hand, adaptive-optics systems designed for diffraction-limited imaging in the IR can improve the resolution in the visible by as much as two times.