| dbo:abstract |
In optics and photography, infinity focus is the state where a lens or other optical system forms an image of an object an infinite distance away. This corresponds to the point of focus for parallel rays. The image is formed at the focal point of the lens. In simple two lens systems such as a refractor telescope, the object at infinity forms an image at the focal point of the objective lens, which is subsequently magnified by the eyepiece. The magnification is equal to the focal length of the objective lens divided by the focal length of the eyepiece. In practice, not all photographic lenses are capable of achieving infinity focus by design. A lens used with an adapter for close-up focusing, for example, may not be able to focus to infinity. Failure of the human eye to achieve infinity focus is diagnosed as myopia. All optics are subject to manufacturing tolerances; even with perfect manufacture, optical trains experience thermal expansion. Focus mechanisms must accommodate part variations; even custom-built systems may have some means of adjustment. For example, telescopes such as the Mars Orbiter Camera, which are nominally set to infinity, have thermal controls. Deviations from its operating temperature are actively compensated to prevent shifts of focus. (en) 無窮遠焦點（infinity focus）為光學及攝影名詞，是指透鏡或其他光學系統的成像在無窮遠處。 一個有二個透鏡的簡單系統（如折射望远镜），無窮遠處的物體會在物镜的焦點成像，再由目鏡放大。放大倍率等於物镜焦距除以目镜焦距。 實務上，不是所有鏡頭都可以設計成焦點在無窮遠處。人的眼睛若無法將焦點調整到無窮遠（或是較遠的距離）稱為近視。 所有光學設備都會受到製造公差的影響，甚至是在無公差的情形下，光學設備也會有熱膨脹的問題。對焦機制需克服這些元件的變異，甚至是客制的系统可能還會有一些调整方法。例如火星軌道器相機平常焦距在無窮遠處，也有針對熱的控制。若操作溫度operating temperature－變化，相機會自動調整，避免焦距偏離。 (zh) |
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無窮遠焦點（infinity focus）為光學及攝影名詞，是指透鏡或其他光學系統的成像在無窮遠處。 一個有二個透鏡的簡單系統（如折射望远镜），無窮遠處的物體會在物镜的焦點成像，再由目鏡放大。放大倍率等於物镜焦距除以目镜焦距。 實務上，不是所有鏡頭都可以設計成焦點在無窮遠處。人的眼睛若無法將焦點調整到無窮遠（或是較遠的距離）稱為近視。 所有光學設備都會受到製造公差的影響，甚至是在無公差的情形下，光學設備也會有熱膨脹的問題。對焦機制需克服這些元件的變異，甚至是客制的系统可能還會有一些调整方法。例如火星軌道器相機平常焦距在無窮遠處，也有針對熱的控制。若操作溫度operating temperature－變化，相機會自動調整，避免焦距偏離。 (zh) In optics and photography, infinity focus is the state where a lens or other optical system forms an image of an object an infinite distance away. This corresponds to the point of focus for parallel rays. The image is formed at the focal point of the lens. In simple two lens systems such as a refractor telescope, the object at infinity forms an image at the focal point of the objective lens, which is subsequently magnified by the eyepiece. The magnification is equal to the focal length of the objective lens divided by the focal length of the eyepiece. (en) |
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Infinity focus (en) 無窮遠焦點 (zh) |
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