本帖最後由 calvin83 於 2018-1-19 00:31 編輯
Fluor Crown glass(低色散玻璃), Fluophosphate glass and Fluorite(fluorspar ,CaF2, 螢石):
Fluophosphate glass and Fluorite(CaF2) 都屬於 Fluor Crown glass(For example, 下圖No. 有N-FK果D(紅圈同附近)). 不過係鏡片用料來講, 只有主要成份為Fluorite(CaF2)先叫會叫螢石.
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二戰前, Fluor Crown glass已經有用係相機鏡頭, 包括著名的Zeiss Sonnar 50/1.5. Fluor Crown glass成份入面係有Fluorite的, 不過同fluorspar色散係可以差好遠. 下面專利上的Fluor Crown glass的Abbe number只係六十幾, fluorspar 係超過九十.
http://onlinelibrary.wiley.com/d ... 944.tb14879.x/epdf?
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Fluophosphate glass, 一種光學特性類似Fluorite的glass, 係二戰時已經有相關研究
https://encrypted.google.com/patents/US2430539
Leica都有唔關於Fluophosphate glass的研究.
https://encrypted.google.com/patents/US3492136
當然, Schott都有出Fluophosphate glass.
http://www.us.schott.com/d/advan ... es-may-2014-neu.pdf
Zeiss以前都有用Fluophosphate glass係APO級長焦.
This 200 mm Aposonnar® T* f/2 telephoto lens from Carl Zeiss with an extremely high speed provides superb image quality. As indicated by the term "Apo", residual chromatic aberration has been drastically reduced - as in the 300 mm Tele-Apotessar® T* f/2.8 lens from Carl Zeiss - by the use of fluophosphate glass resulting in such superb sharpness and brilliance.
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1886年, Zeiss 用係顯微鏡的apochromatic objectives已經用緊天然fluorspar…
Artificial Fluorite 的研究係二十年代已經開始, 二戰時美國已經成功左整到較大塊的Artificial Fluorite. 不過要去到1969年先由Canon開始大量用係相機鏡頭.
https://www.osapublishing.org/josa/abstract.cfm?uri=josa-39-9-731
Canon同Nikon將低色散玻璃分為幾種 :
Canon: UD, Super UD, Fluorite
Nikon: ED, Super ED, Fluorite
Canon
http://cpn.canon-europe.com/cont ... al_and_ud_lenses.do
NIKKOR Technology Movie
https://youtu.be/_wBRmmEExpY?t=2m59s
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From https://www.clublexus.com/forums ... al.html#post3101289
Caf2 versus ED glass in terms of scatter.
Caf2 will easily win for light transmission as well as contrast, all else being equal.
This is from the Telescope Engineer Co newsgroup.
Caf2 同 ED係 scattering(散射)上比較, Caf2 散射輕微好多.
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最後, 一般35mm 格式的相機鏡頭, 標準鏡同廣角鏡係唔會用上Fluorite的.... 因為個根本唔需要用Fluorite已經可以有效修正secondary chromatic aberration. Fluorite主要都係用係長焦上. |
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發表於 2018-1-18 16:32
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