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How to polish optical lens
Glass that can change the direction of light propagation and can change the relative spectral distribution of ultraviolet, visible or infrared light. According to optical characteristics, optical glass can be divided into: colorless optical glass, anti-radiation optical glass, radiation resistant optical glass, colored optical glass, ultraviolet and infrared optical glass, and optical quartz 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 formula. In order to ensure the transparency of glass, it is necessary to strictly control the content of colored impurities, such as iron, chromium, copper, manganese, cobalt, and nickel. When ingredients are required, accurate weighing and uniform mixing are required.
The primary production process is smelting, forming, annealing and inspection.
①, there are single crucible batch smelting method and tank kiln (see kiln) continuous smelting method. Single crucible smelting method can be divided into optical lens clay crucible smelting method and platinum crucible smelting method.
②, the molding methods of molding optical glass include classical crucible method, rolling method and pouring method, but nowadays, leakage molding is more and more widely used (using single crucible (Or continuous melting and flowing 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, it is necessary to formulate a strict annealing system and perform fine annealing.
④. The objectives of inspection and measurement are: optical constants, optical uniformity, stress birefringence, fringes, bubbles, etc.
Due to the rapid development of modern science and technology, the scribing of optical zero crystals, sapphire and other surfaces shows that the demand for additional parts on the indenter is not only increasing in number, but also When the precision requirements are smaller and the scribing speed of the optical lens is higher, the brittle and hard materials are getting higher and higher like gold, which promotes the continuous plastic processing of the traditional optical processing technology, and there will be continuous on the surface of the test piece. Development and change, for a long time, optical parts processing is the use of continuous slender chips and smooth and transparent dents. System of grinding and polishing methods.
The lens is made by optical processing. Today we will look at how to polish the lens by optical processing.
After the optical lens is finely ground with a grinding fluid, there is still a crack layer about 2–3m thick on the surface. The method to eliminate this crack layer is polishing. The mechanism of polishing is the same as that of lapping, except that the tool material used is different from slurry. The materials used for polishing include cloth, polyurethane and pitch. The focusing lens usually has to achieve High-precision polished surface, the most commonly used material is high-grade polished asphalt. The use of asphalt for polishing is to drive the polishing liquid to grind the surface of the lens to generate heat through the fine surface of the asphalt, so that the glass melts and flows, melts away the rough vertices and fills in the valley bottom of the cracks, and gradually removes the crack layer.
Currently, the polishing powder used for polishing glass lenses is mainly cerium oxide (CeO2). The proportion of the polishing solution varies according to the polishing period of the lens. Generally, the initial stage of polishing Use a high-concentration polishing liquid when combined with the polishing mold. After the lens surface is bright, use a thinner polishing liquid to avoid orange peel on the mirror surface (fogging of the lens surface).
The movement mechanism used for polishing and grinding is the same. In addition to the different polishing tools and working fluids, the environmental conditions required for polishing are also stricter than those for aspheric mirrors. The general points to note during polishing are as follows:
There should be no impurities in the surface of the polishing asphalt and the polishing liquid, otherwise it will cause scratches on the mirror surface.
The polished asphalt surface must match the surface of the lens, otherwise it will be bounced during polishing, which will bite the polishing powder and scratch the surface of the lens.
Before polishing, it must be determined whether there are scratches or punctures on the surface of the lens after polishing.
Whether the size and material of the polishing tool are appropriate.
Whether the hardness and thickness of the asphalt are appropriate.
During the polishing process, you must always pay attention to the condition and accuracy of the lens surface. In the inspection of lens surface defects, because the inspection process is judged by personal vision and methods, the inspector should have a deep understanding of the specifications of scratches and sand holes, and often compare the standard samples of scratches and sand holes. To ensure the correctness of the inspection.