Eyepieces目镜
The eyepiece for many optical instruments is a simple magnifier. Because of aberrations, a single lens is not adequate for the eyepiece of a high quality optical instrument, and many lens combinations have been developed to minimize the aberrations. A sample is shown here. 许多光学仪器的目镜通常是一个简单的放大镜。由于像差的存在，单一透镜不足以作为高质量光学仪器的目镜，因此发展出了多种透镜组合以最小化像差。一个示例如图所示。
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Index Multi-element lenses 索引多元件透镜 | ||
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Ramsden Eyepiece拉姆森目镜
In the Ramsden eyepiece, the two lenses are made of the same kind of glass, e.g., spectacle crown. The lenses are of equal focal length and their separation is equal to the focal length. The field lens coincides with the first principal plane, which is convenient for the placing of crosshairs or reticules, but inconvenient in that it highlights any dust on the lens. 在拉姆森目镜中，两个透镜由同一种玻璃制成，例如眼镜冠玻璃。两个透镜的焦距相等，它们的间距等于焦距。场透镜与第一个主平面重合，这便于放置十字丝或测微尺，但缺点是会突出显示任何在透镜上的灰尘。
This eyepiece is effective in reducing chromatic aberration , doing a better job with longitudional achromatism than with lateral. Its approach to minimizing chromatic aberration is based on spacing the lens pair so that dependence upon the index of refraction is minimized. It is quite effective in reducing spherical aberration and distortion, and removes the problem of coma. 这种目镜在减少色差方面很有效，其在纵向消色差方面比在横向消色差方面更有效。它通过将透镜对间距设置，以最小化折射率的依赖性来最小化色差。它在减少球面像差和畸变方面也很有效，并解决了彗差的问题。
In standard use, the objective lens will form an image at the first surface of the field lens. 在标准使用中，物镜透镜会在场透镜的第一表面形成像。
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Index Lens concepts "Reference Meyer-Arendt Ch 9, 4th Ed. 索引透镜概念 参考Meyer-Arendt第9章，第4版 | ||||||||||
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Orthoscopic Eyepiece正像目镜
This eyepiece is characterized by its wide field of view and high magnification. It finds application in high-power telescopes and range finders. It corrects well for distortion. The triplet corrects well for chromatic aberration. 这种目镜以其宽视场和高放大率而著称。它被应用于高功率望远镜和测距仪中。它能很好地校正畸变。三组透镜能很好地校正色差。
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Index Lens concepts "Reference Meyer-Arendt Ch 9 索引透镜概念 '参考Meyer-Arendt第9章 | ||||||||||
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Erfle Eyepiece厄弗莱目镜
This eyepiece has two achromatic doublets, even three in some variations. Its wide field of view (up to 70°) enhances its use in high quality astronomical telescopes. 这个目镜包含两个消色差双组，某些变种可能有三个。其宽视场（最高可达70°）使其在高质量天文望远镜中得到广泛应用。
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Index Lens concepts "Reference Meyer-Arendt Ch 9 索引透镜概念 '参考Meyer-Arendt第9章 | ||||||||||
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