GB/T 903-2019Colourless optical glass (English PDF)

3.1 Environment friendly colorless optical glass

The optical glass, which has a total amount of environmentally hazardous impurities caused by impurities in chemical raw materials or furnace materials and processes as follows: lead (Pb) <= 100 mg/kg, arsenic (As) <= 100 mg/kg, cadmium (Cd) <= 5 mg/kg, mercury (Hg) <= 100 mg/kg, hexavalent chromium (Cr6+) <= 100 mg/kg.

3.2 Color cord

lambda80/lambda5 The ratio -- of the wavelength lambda80 corresponding to the spectral transmittance of 80% of optical glass (thickness of 10 mm ± 0.1 mm) TO the wavelength lambda5 corresponding to the spectral transmittance of 5%. When ne >= 1.85, the wavelength lambda70 corresponding to the spectral transmittance of 70% is used, instead of lambda80.

Example: When the spectral transmittance is 80%, the corresponding wavelength is 367 nm; when the spectral transmittance is 5%, the corresponding wavelength is 323 nm; THEN, lambda80/lambda5 is 37/32.

3.3 Inclusions

Foreign impurities or foreign matter, which is present in optical glass.

Note: For example, bubbles, grains, nodules, stones, platinum particles.

4.4 Marking

4.4.1 Marking method

It consists of three parts: Optical glass grade, smelting batch number, standard number.

4.4.2 Marking example

The optical glass, which is designated H-K9 AND has the melting batch number G0220091105, is marked as follows: Colorless optical glass GB/T 903-2019-G0220091105 H-K9

5.1 Specifications, dimensions, surface quality

5.1.1 Strip (bar) material's specification tolerance

Length tolerance: It shall be less than or equal to 20 mm.

Width tolerance: It shall be less than or equal to 2 mm.

Center thickness tolerance: It shall be less than or equal to 3 mm.

5.1.2 Tolerance of round (bar) material

Round bar length tolerance: It shall be less than or equal to 20 mm.

5.1.3 Surface quality of strip (bar) material

The surface of the strip (bar) material is naturally smooth; OR after grinding, the depth of surface defects (including bumps, burst points, ripples, cracks, inclusions, etc.) shall be less than or equal to 0.5 mm.

5.1.4 Blocks

5.1.4.1 Single block supply: If the side length is less than 100 mm, the tolerance range of each side shall be not more than 3 mm; if the side length is not less than 100 mm, the tolerance range of each side shall be not more than 5 mm.

5.1.4.2 Multiple block supply: According to the multiple side length, the tolerance provisions of 5.1.4.1 shall be implemented. […]

6.1 Specifications, dimensions, surface quality

The specification tolerance of optical glass is measured with a steel ruler, which has a division value of 1 mm. Visually check the surface defects.

6.2 Environmentally hazardous substances

For the indicators of environmentally hazardous substances in environmentally friendly colorless optical glass, the acid dissolution method can be used to treat the sample; use the inductively coupled plasma emission spectroscopy (ICP-AES) or atomic absorption spectroscopy (AAS) or atomic fluorescence spectroscopy (AFS), to carry out analysis.

It may also directly grind the environmentally friendly glass into a flat plate; use X-ray fluorescence spectroscopy for analysis.

6.3 Refractive index, dispersion coefficient, batch deviation

The refractive index, dispersion coefficient, batch deviation of optical glass are tested according to the method of GB/T 7962.1-2010. The measurement uncertainty of refractive index is ±5 x 10^-5.

6.4 Optical uniformity

The optical uniformity of optical glass is tested, according to the method of GB/T 7962.2-2010.

6.5 Stress birefringence

The stress birefringence of optical glass is tested, according to the method of GB/T 7962.5-2010.

6.6 Streak degree (projection method)

There are two types of streak detection methods:

a) Streak degree detection method 1: The principle is as shown in Figure 1. S is the monochromatic light source; D is the fine frosted glass immersion screen; A is the pinhole aperture, which is located at the back focal point of the collimating achromatic lens L1; B is the movable cross slit, which is located on the back focal plane of the objective lens L2. The sample to be tested is placed at point P, so that its polished surface is perpendicular to the line of sight. The light deflection and drift, which is caused by the slight non-parallelism of the polished surface, are compensated by a movable cross slit. The cross slit shall be adjusted, so that the […]

6.7 Inclusions

The inclusions of optical glass are tested, according to the method of GB/T 7962.8-2010.

6.8 Color cord, light absorption coefficient

The optical absorption coefficient of optical glass is tested, according to the method specified in GB/T 7962.9-2010. Color cord test of optical glass: use the samples which have a thickness of 10 mm ± 0.1 mm; grind the two opposite surfaces to be parallel; use a spectrophotometer to test the transmittance (including surface reflection loss), according to the method of GB/T 7962.12-2010. Respectively use lambda80(70) and lambda5, to represent wavelengths at a transmittance of 80% (70%) and 5%.

6.9 X-ray resistance

The X-ray resistance of X-ray-resistant optical glass is tested, according to the method of GB/T 7962.10-2010.

6.10 Physical-chemical properties

The acid resistance of optical glass is tested, according to the method of GB/T 7962.14-2010; the moisture resistance is tested, according to the method of GB/T 7962.15-2010; the linear expansion coefficient, transition temperature, relaxation temperature are tested, according to the method of GB/T 7962.16-2010; Knoop hardness is tested, according to the method of GB/T 7962.18-2010; density is tested, according to the method of GB/T 7962.20-2010.

7.1 General

Inspection is divided into exit-factory inspection and type inspection.

7.2 Exit-factory inspection

Optical glass is supplied in batches. A batch of optical glass blanks shall consist of the same designation, smelting batch number, annealing number.

7.3 Type inspection

Type inspection shall be carried out, in one of the following situations:

a) When the product is subject to type finalization OR trans-plant production;

b) After formal production, where there are major changes in raw materials, formulas and processes, which may affect product performance;

8.2.1 Labels for packing box

The labels for packing box shall have the following markings:

a) Optical glass's designation, melting number;

b) Specification and mass (kg).

8.2.2 Product certificate

The product certificate shall have the following marks:

a) Qualification seal;

b) Optical glass's designation, melting number;

c) Contract number;

d) Some properties and some technical indicators, such as: refractive index nd, dispersion coefficient upsilon d, density rho, bubble degree, streak degree, stress birefringence, color cord, etc.;

e) Optical density increment of X-ray resistant glass.

9.1 Packaging

It is packed in qualified carton or wooden box; each piece of glass shall be separated by cardboard to avoid collision; there shall be no looseness in the box. The packaging shall be intact, the box surface is clean, the handwriting is clear, the text is consistent with the content. Each batch of glass shall be accompanied by a product certificate.

9.2 Transportation and storage

9.2.1 When the glass is stacked, the upper and lower glasses shall be separated by a cardboard.

9.2.2 When transporting or storing, it shall be rain-proof and moisture-proof; handle with care; do not collide. […]