Optical glass of low dispersion and low refractive index WordNet 3.0 & Open English WordNet

Crown glass is a type of optical glass used in lenses and other optical components. Wikipedia

Type of optical glass used in lenses. Wikipedia Disambiguation

Type of glass Wikidata

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. Wiktionary

Variety of optical glass. Wiktionary (translation)