Crown glass (optics)
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Crown glass is type of optical glass used in lenses and other optical components.
Crown glass is produced from alkali-lime silicates containing approximately 10% potassium oxide. It has low refractive index (≈1.52) and low dispersion (with Abbe numbers around 60).
As well as the specific material named "crown glass", there are other optical glasses with similar properties that are also called crown glasses. Generally, this is any glass with Abbe numbers in the range 50 to 85. For example, the borosilicate glass Schott BK7 is an extremely common crown glass, used in precision lenses. Borosilicates contain about 10% boric oxide, have good optical and mechanical characteristics, and are resistant to chemical and environmental damage.
Other additives used in crown glasses include zinc oxide, phosphorus pentoxide, barium oxide, and fluorite.
See also
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