BK7 is the brand of Schott glass factory in Germany, and K9 is the corresponding domestic glass brand. N-bk7 is the glass of German Schott, h-k9l is the glass of Chengdu Guangming, and bsc7 is the glass of Hoya in Japan
BK7 has been used in lenses or prisms since a long time ago. Although there are bsc7 or bsl7 and other models due to different manufacturers, the composition, optical properties, physical properties and chemical properties are basically the same. The invisible region has little effect on the optical uniformity and refractive index of the system. In addition to lenses or prisms, they are also used in most optical elements such as reflector or spectroscope substrates or various coated filter substrates.
