The difference between optical glass and other glass is that it is a part of the optical system and must satisfy the requirements of optical imaging. Therefore, the determination of the quality of optical glass also includes some special and more stringent indicators.

Today, we talk about the importance of optical glass must have a high degree of transparency.

The relationship between the brightness of the optical system and the transparency of the glass. Optical glass to a certain wavelength of light transparency in the light absorption coefficient K. Light passes through a series of lenses and lenses, whose energy is partially absorbed by the interface of the optical part and the other part is absorbed by the medium (glass). The former with glass refraction rate increases, the high refractive rate of glass this value is very large, such as the heavy flint glass surface optical reflection loss of about 6%. Therefore, the main way to improve the transmission efficiency is to reduce the reflection loss on the surface of the lens, such as the coating surface coating, and so on. For large size optical components such as the telescope's objective, due to its great thickness, the optical system's transmission rate is mainly determined by the optical absorption coefficient of the glass itself. By improving glass raw material purity and in the whole process from the ingredients to the melting prevent any coloring impurities mixed, generally can make optical glass optical absorption coefficient less than 0.01 (i.e., thickness is 1 cm glass to light through rate is more than 99%).