There are many kinds of glass, one of which is optical glass, which can change the propagation direction of light. It is widely used in lenses and prisms of optical instruments. Optical glass must meet the requirements of optical imaging. It is no higher than ordinary glass and has higher requirements for the quality of optical glass. For qualified optical glass, it shall meet the following requirements.
Firstly, the optical constants of optical glass and the same batch of glass shall be consistent, * a variety of optical glass has specified standard refractive index values for different wavelengths of light, which can be used as the basis for optical designers to design optical systems.
Therefore, the optical constants of the optical glass produced by the factory must be within a certain allowable deviation range of these values, otherwise the actual imaging quality will be inconsistent with the expected results in the design, which will affect the quality of the optical instrument. At the same time, because the same batch of instruments are often made of the same batch of optical glass, in order to facilitate the unified correction of instruments, the allowable deviation of refractive index of the same batch of glasses is more strict than their deviation from the standard value.
Secondly, it needs a high degree of transparency. The brightness of the optical system is proportional to the transparency of the glass. The transparency of optical glass to light of a certain wavelength is measured by light absorption coefficient K λ express. After light passes through a series of prisms and lenses, part of its energy is lost in the interface reflection of optical parts, and the other part is absorbed by the medium (glass) itself. The former increases with the increase of glass refractive index. For high refractive index glass, this value is very large. For example, for heavy flint glass, the light reflection loss on one surface is about 6%.