According to the scope of application, optical glass is generally divided into colorless optical glass and colored optical glass. For different types, whether domestic or foreign, optical glass has different brand naming principles, and each country has different brand numbers and glass codes.
The grade of colorless optical glass consists of three parts, and the following is illustrated by taking the optical glass grade of the famous Schott company as an example.
The first letter
Generally marked as "N-", "P-" or missing, it represents whether the glass is environmentally friendly. Among them, N- represents that the glass is free of volatile harmful substances such as lead (Pb) and arsenic (As), which is environmentally friendly glass, and China's optical glass is represented by "H-", and Japan's Ohara company is represented by "S-". "P-" (represented by "L-" by Ohara) represents that this kind of glass has a low glass transition temperature Tg (the temperature corresponding to the transition of amorphous objects from glass to high elasticity), so it is easy to be precision machined and molded, and all "P-" glass is also environmentally friendly glass that does not contain lead and Shen; The missing brand glass is the traditional optical glass that contains lead and shen.
The second letter
The types of glass are represented, which are: F flint, K crown, B boron, BA barium, LA lanthanum, P phosphorus, Z zinc, S heavy, L light, SS super heavy, LL super light. The "lightness" of glass refers to the level of its refractive index, such as SK refers to crown glass, and LAF refers to flint glass containing earth lanthanum.
Part III
It is usually expressed by a number to distinguish different subclasses of the same type of glass, and the level of the number is in principle related to the refractive index of the glass. All optical glasses also have a worldwide numerical designation, AB.C.
- A is the refractive index nd, which represents three decimal places;
- B is the Abbe number and the first three digits of RD;
- C represents the first three digits of the glass density;
The code of N-SF5 glass is 673323.286, which means that the glass is heavy flint, with a refractive index nd=l.673, Abbe number rd=32.3, and a density ρ=2.86g/cm3.
The glass code of N-BK7 is 517642.251, which represents its refractive index nd=1.517, Abbe number rd=64.2, and density ρ=2.51g/cm3.
The Abbe number is an exponent used to express the dispersion capacity of a transparent medium. In general, the greater the refractive index of the medium, the more severe the dispersion and the smaller the Abbe number; Conversely, the smaller the refractive index of the medium, the slighter the dispersion, and the larger the Abbe number.
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