- MACHINE VISION LENSES
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- PRECISION OPTICS
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The production process of optical glass
The raw materials for the production of optical glass are some oxides, hydroxides, nitrates and carbonates, and phosphates or fluorides are introduced according to the requirements of the formulation. In order to ensure the transparency of glass, the content of colored impurities, such as iron, chromium, copper, manganese, cobalt, nickel, etc., must be strictly controlled. When ingredients are required, accurate weighing and uniform mixing are required. The main production processes are smelting, forming, annealing and inspection.
1. There are single crucible batch smelting method and tank kiln (see kiln) continuous smelting method for smelting. Single crucible smelting method can be divided into clay crucible smelting method and platinum crucible smelting method. No matter what kind of smelting method is used, it needs to be stirred with a stirrer, and the temperature and stirring are strictly controlled to make the glass liquid reach a high degree of uniformity. Clay crucible can smelt most crown glass and flint glass, with low cost, and is used when the melting temperature of the glass exceeds the service temperature of platinum. The platinum crucible can smelt high-quality glass that has a serious corrosive effect on the clay crucible, such as heavy crown, heavy barium flint, rare earth glass and fluorophosphorous glass. The platinum crucible is heated by electricity, generally a silicon-carbon rod or silicon-molybdenum rod electric furnace is used. However, high-frequency heating can be used to manufacture glass that has a high tendency to crystallize, requires rapid cooling, and has certain requirements on the atmosphere.
Since the 1960s, various countries have successively adopted platinum-lined continuous tank smelting to greatly increase the output and quality of optical glass. This is the main trend in the development of optical glass production technology.
2. The molding methods for molding optical glass include the classical crucible method, the rolling method and the pouring method. However, leakage molding (using a single crucible (Or continuous melt flow out of the material liquid), can directly draw rods or drop material to form large-size blanks, improve the utilization rate of gobs and the yield rate.
3. Annealing In order to eliminate the internal stress of the glass to the greatest extent and improve the optical uniformity, a strict annealing system must be formulated for precision annealing.
4. The indicators for inspection and measurement include: optical constants, optical uniformity, stress birefringence, fringes, bubbles, etc.
The raw material of optical glass is high-quality quartz sand as the main material, and auxiliary materials are appropriately added. Due to the high refractive index, low dispersion and good chemical stability of rare earths, optical glass can be produced, which can be used to make lenses for advanced cameras, video cameras, telescopes and other advanced optical instruments. For example, a kind of lanthanum glass with excellent optical properties containing lanthanum oxide lao360% and b2o340% oxide is an indispensable optical material for manufacturing high-end camera lenses and periscope lenses. In addition, using the radiation protection properties of some rare earth elements, radiation protection glass can be produced.