An inorganic glassy material that transmits light by refraction, reflection and transmission or changes the intensity or spectral distribution of light by absorption is called optical glass. It has stable optical properties and high optical uniformity. Optical glass has high transparency, high homogeneity in chemistry and Physics (structure and performance), and specific and accurate optical constants. It can be divided into silicate, borate, phosphate, fluoride and chalcogenide series. They are classified according to their position in the refractive index (nd) - Abbe value (VD) diagram. Traditionally, the glasses with Nd > 1.60, VD > 50 and nd < 1.60, VD > 55 are classified as crown (k) glass, and the others as flint (f) glass. Coronal glass is generally used as convex lens, flint glass as concave lens.
Optical glass is the foundation and important part of optoelectronic technology industry. Especially after the 1990s, with the continuous integration of optics, electronic information science and new material science, the application of optical glass, as the basic material of optoelectronics, in the three fields of optical transmission, optical storage and optoelectronic display, has developed rapidly, and has become one of the basic conditions for the development of social informatization, especially optoelectronic information technology. With the sustained and stable development of domestic economy, China's optical glass manufacturing industry is developing rapidly.
In fact, the development of optical glass and optical instruments are inseparable. The new reform of optical system often puts forward new requirements for optical glass, thus promoting the development of optical glass. Similarly, the success of trial production of new glass often promotes the development of optical instruments.
Optical lens laser lens is made of optical glass, generally refers to the lens that can pass through and adjust the visible light. The optical lens must be measured by optical instruments to check whether the purity, transparency, uniformity, refractive index and dispersion index meet the specifications. The qualified glass block is heated and forged to form optical lens hair. There is still a thick crack layer on the surface of optical lens after fine grinding with grinding solution. The method to eliminate the crack layer is polishing.
After the optical lens is finely ground by grinding solution, there is still a crack layer about 2 – 3 m thick on its surface. The method to eliminate the crack layer is polishing. The mechanism of polishing and grinding is the same, but the material used is different from that of slurry. The materials used for polishing are cloth, polyurethane and pitch. Generally, high-precision polishing surface is achieved, and the most commonly used material is high-grade polishing pitch. The use of asphalt for polishing is to drive the polishing solution to grind the lens surface to generate heat through the fine surface of asphalt, so that the glass can melt and flow, remove the rough vertices and fill the bottom of the crack, and gradually remove the crack layer. At present, cerium oxide (CeO2) is the main polishing powder used for polishing glass lenses. The proportion of the polishing solution varies according to the polishing period of the lenses. Generally, a higher concentration of polishing solution is used in the initial stage of polishing, and a thinner concentration of polishing solution is used after the surface of the lenses is bright, so as to avoid orange peel phenomenon (lens surface atomization).