Colorless optical glass of optical materials

1. Series and classification

Colorless optical glass is divided into two series: ordinary optical glass series (P series) and radiation resistant optical glass series (N series).

Classification of colorless optical glass: According to the refractive index nd and the dispersion coefficient vd according to the position in the nd-vd field map, they are divided into 18 categories, as shown in Table 1 below.

Table 1 Classification of colorless optical glass

2. Brand

In the same kind of optical glass, according to the difference of its refractive index nd, central dispersion np-nc and dispersion coefficient vd, it is distinguished by serial numbers 1, 2, 3... etc. after the code, such as K1, K2, K3... etc. Etc., K1, K2, K3, etc. are called grades.

3. Quality index

The quality indicators of colorless optical glass include: the allowable difference between the refractive index nd, the dispersion coefficient vd and the standard value. The consistency of the refractive index and the dispersion coefficient in the same batch of glass; optical uniformity; stress birefringence; fringe degree; bubble degree ; Light absorption coefficient, etc. (These are easily found in the drawings of optical parts) In the national standard for colorless optical glass, they are classified and graded according to the difference between them and the specified values.

4. Radiation resistant optical glass

After being irradiated by x-rays or γ-rays, optical glass with a certain degree of anti-radiation stability is called radiation-resistant optical glass.

The classification of radiation resistant optical glass is the same as the above-mentioned colorless optical glass. Its brand is formed by adding its radiation resistance to the above-mentioned ordinary colorless optical glass. For example, K9 glass can withstand X-ray irradiation of 1×105 Roentgen, it is called K509, and so on.

5. Physical and chemical properties of some optical glass

Refractive index nd, relative grinding hardness FA, chemical stability, density and microhardness of optical glass can be found in related data. Table 3 shows a small amount of commonly used glass data (hard work, inform and Chen crystal in advance when COPY).

The relative grinding hardness FA in the table refers to the grinding hardness of the tested glass relative to the standard glass (K9) under the same grinding conditions. It is expressed by the ratio A of the grinding volume of the standard glass sample (the volume being ground) to the grinding volume (the volume being ground) of the tested glass sample

A=V0/V

Where V0——the volume of the standard glass sample to be ground (cm³);

V ——the volume of the glass sample being ground (cm³).

The microhardness in the table indicates the ability of the glass to resist the intrusion of hard objects, and it is expressed by the Kjeldahl microhardness HK.

The moisture resistance stability test in the table in the table is to place the polished glass sample on both sides under saturated water vapor conditions at 70±1℃. After seven days and nights, measure the surface scattering rate TB (with a device for measuring the scattering of the glass surface). When light trapping), compared with the scattering rate TA of a standard white board, that is

H=(TB/TA)×100%

The H value (turbidity value) means the "haze generation rate" of the glass surface.

The classification of moisture resistance stability is determined by comparing the H value of the tested sample with the H value of the standard samples BaK7 and ZK9 under the above conditions. There are 1, 2, 3, and 4 levels.

The acid resistance stability test in the table uses acetic acid with an acidity of pH 2.9, standard acetate with pH 4.6, and water with pH 6.0 as the measuring medium. After the surface of the polished glass sample is corroded by the medium, observe the glass surface under an incandescent lamp The time when the purple-blue interference color appears (the optical thickness of the erosion and damage layer is 135nm at this time) or the time when the surface appears mottled or peeled off can be used to classify and grade the acid resistance of the optical glass in a descending manner, as shown in Table 2.