英和和英

名詞

crown glass (usually uncountable, 複数形 crown glasses)

1. An early type of window glass made by blowing glass into a hollow globe (crown) and then flattening it on a punty, reheating and spinning out into a flat disk by centrifugal force.
2. (optics) A variety of glass used in lenses and other optical components due to its low refractive index and dispersion. Originally crown glass was made from alkali-lime silicates with approximately 10% potassium oxide, but similar properties may be attained with other recipes.

   The convex half of an achromatic lens is composed of crown glass.

参考

• bullseye

外部リンク

• Crown glass (window) on Wikipedia.
• Crown glass (optics) on Wikipedia.