There are many types of glass, among which optical glass is one of them, which can change the direction of light propagation. It is used for lenses, prisms, etc. in optical instruments. Optical glass must meet the imaging requirements of light, and it does not require higher quality than ordinary glass. Qualified optical glass needs to meet the following requirements.
Firstly, the optical constants of optical glass and the same batch of glass must be consistent. The first type of optical glass has a specified standard refractive index value for different wavelengths of light, which serves as the basis for optical designers to design optical systems.
So the optical constants of the optical glass produced by the factory must be within a certain allowable deviation range of these values, otherwise it will cause the actual imaging quality to deviate from the expected results during design and affect the quality of the optical instrument. At the same time, due to the fact that instruments of the same batch are often made of the same batch of optical glass, in order to facilitate unified calibration of the instruments, the allowable deviation of the refractive index of the same batch of glass should be more stringent than their deviation from the standard value.
Secondly, it requires a high degree of transparency, and the brightness of the optical system imaging is proportional to the transparency of the glass. The transparency of optical glass to a certain wavelength of light is represented by the light absorption coefficient K λ. After passing through a series of prisms and lenses, some of the energy of light is lost at the interface reflection of optical components, while the other part is absorbed by the medium (glass) itself. The former increases with the increase of glass refractive index, and this value is very large for high refractive index glasses, such as heavy flint glass, where the surface light reflection loss is about 6%.