Abbe Number In physics and optics, the Abbe number, also known as the V-number or constringence of a transparent material, is a measure of the material's dispersion (variation of refractive index with wavelength). It is named for Ernst Abbe (1840-1905), the German physicist who defined it. The Abbe number V of a material is defined as: V=(nD-1)/(nF-nC) where nD, nF and nC are the refractive indices of the material at the wavelengths of the Fraunhofer D-, F- and C- spectral lines (589.2 nm, 486.1 nm and 656.3 nm respectively). Low dispersion materials have high values of V. Abbe numbers are used to classify glasses. For example, flint glasses have V<50 and crown glasses have V >50. Typical values of V range from around 20 for very dense flint glasses, up to 65 for very light crown glass, and up to 85 for fluor-crown glass. Abbe numbers are only a useful measure of dispersion for visible light, and for other wavelengths, or for higher precision work, the group velocity dispersion is used. 以上摘取自 http://www.answers.com/topic/abbe-number 文中提到螢石的阿貝數極高，對相機有些興趣的，知道Canon對於 自家高檔鏡頭L鏡都會用fluorite來減低色散，那一般市面上的鏡 片有使用這種材質來製造嗎?如果沒有是因為價錢的因素無法量產 還是本身技術無法實行呢? 感謝回答 ※ 引述《TOUCH99 ( )》之銘言： : 前幾篇那個推文講到一些有關阿貝數(ABBE NUMBER)的事情 : 發現板上好像沒有相關文章,我根據我的認知拋磚引玉的大家來討論一下!! : 阿貝數和折射率都是光學上兩個相當的重要的參數!! : 折射率大家有學過國中理化的應該都清楚,折射率對你的眼睛會產生什麼作用 : 阿貝數就是對同一個眼睛對於不同頻率的光會產生不一樣的折射率 : 大家常說的色散就是因此而產生的!!另外阿貝數越大越不容易產生色散 : 一般說來樹酯鏡片有很多曲折率,曲折率越大,阿貝數越小 : 這個問題一直是目前各大光學廠想要努力改進的目標,一般說來阿貝數40以上就算很好了! : 玻璃鏡片的阿貝數通常也比安全鏡片高一些 XD -- 愛錢的女人只給凱子摸 不懂得用保險套的人別嫌孩子多 金錢力量雖大　卻生不帶來死不帶走 --

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