After the optical lens is finely ground by the 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 and grinding is the same, but the tool material used is different from the slurry (slurry). The materials used for polishing are cloth, polyurethane, and pitch. Usually, high precision is required. Polished surface, the most commonly used material is high-grade polished asphalt.
Optical lenses are polished with asphalt. The fine surface of asphalt drives the polishing liquid to grind the surface of the lens to generate heat, melt the glass, melt away the rough vertices and fill the bottom of the crack, and gradually remove the crack layer. At present, the polishing powder used for polishing glass lenses is mainly cerium oxide (CeO2). The proportion of the polishing liquid is different according to the polishing period of the lens. Generally, a higher concentration of polishing liquid is used in the initial polishing and when the mold is combined with the polishing mold. After the lens surface is bright, use a thinner polishing solution to avoid orange peel (fogging of the lens surface).
The motion mechanism used for polishing and polishing is the same. Except that the polishing tool is different from the working fluid, the required environmental conditions during polishing are also stricter than during polishing. The general matters to be noted when polishing are as follows: there must be no impurities in the surface of the polished asphalt and the polishing liquid, otherwise it will cause scratches on the mirror surface. The surface of the polished asphalt must be consistent with the surface of the lens, otherwise it will bounce during polishing, so the polishing powder will be bitten and the lens surface will be scratched.
Before polishing, you must determine whether the lens surface has scratches or punctures left after grinding. Whether the size and material of the polishing tool are appropriate. Whether the hardness and thickness of asphalt are appropriate. During the polishing process, it is necessary to pay attention to the condition and accuracy of the lens surface at any time. The inspection of lens surface defects, because the inspection process is judged by personal vision and methods, so 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.