The main production process of optical glass.
The raw materials for the production of optical glass are some oxides, hydroxides, nitrates and carbonates, and phosphate or fluoride are introduced according to the requirements of the formula. In order to ensure the transparency of glass, the content of coloring impurities must be strictly controlled, such as iron, chromium, copper, manganese, cobalt, nickel, etc. Accurate weighing and uniform mixing are required during batching. The main production processes are melting, forming, annealing and inspection.
1. Smelting: there are single crucible batch smelting method and tank kiln (see kiln) continuous smelting method. Single crucible smelting method can be divided into clay crucible smelting method and platinum crucible smelting method. No matter what smelting method is adopted, it needs to be stirred with a stirrer, and the temperature and stirring shall be strictly controlled to make the glass liquid highly uniform. Clay crucible can melt most crown glass and flint glass with low cost, and can be used when the melting temperature of glass * the service temperature of platinum. Platinum crucible can melt glass with high quality and serious erosion to clay crucible, such as heavy crown, heavy barium flint, rare earth glass and fluorine phosphorus glass. Platinum crucible is electrically heated, generally using silicon carbide rod or silicon molybdenum rod electric furnace. However, high frequency heating can be used to manufacture glass with large crystallization tendency, requiring cooling and certain requirements for atmosphere.
Since the 1960s, countries have successively adopted continuous tank furnace smelting lined with platinum, which has greatly improved the output and quality of optical glass, which is the main trend of the development of optical glass production technology.
2. Molding: the molding methods of optical glass include classical crucible breaking method, rolling method and pouring method, but at present, leakage molding (using single crucible or continuous melting to flow out the material liquid) is more and more widely used, which can directly pull the rod, drop the material, press the mold or leak the material to form large-size blanks, so as to improve the utilization rate and yield of material drops.
3. Annealing: in order to * eliminate the internal stress of the glass to a great extent and improve the optical uniformity, we must * * strict annealing system and carry out precision annealing.
4. Inspection: the measured indexes include: optical constant, optical uniformity, stress birefringence, fringe, bubble, etc.
Optical glass can change the propagation direction of light and the relative spectral distribution of ultraviolet, visible or infrared light.
In a narrow sense, optical glass refers to colorless optical glass.
In a broad sense, optical glass also includes colored optical glass, laser glass, quartz optical glass, anti radiation glass, ultraviolet infrared optical glass, fiber optical glass, acoustooptic glass, magneto-optical glass and photochromic glass. Optical glass can be used to manufacture lenses, prisms, mirrors and windows in optical instruments.