Classification of lens materials:
Glass lenses, including optical glass lenses and high refractive index lenses (commonly known as ultra-thin filter), have high hardness and good wear resistance. Generally, their quality and parameters do not change with time, but the impact resistance and weight of glass lenses are slightly inferior to resin lenses.
Resin lenses are generally much lighter than glass lenses, and the impact resistance is better than glass, uv protection, but its surface hardness is lower, more easy to be scraped. Resinous lens and lens of coating film because its characteristic is softer, should notice to do not let lens face contact hard thing at ordinary times so, had better use clear water first when scrub (or mix a few wash clean essence) clean, try cloth or high-quality cotton paper to absorb the water drop on lens with special next. In addition, in poor environmental conditions should be careful to use coated lenses, so as to avoid contamination difficult to clean.
Cosmos (PC) lens: high index of refraction, strong, but easy to wear. Most used for children's lenses, frameless assembly or athlete's eye protection.
Spherical lens and aspheric lens:
In the traditional optial spherical lens, not only the lens is thicker, but also things are distorted through the periphery of the lens, which is called aberration. Through the spherical lens to observe the wearer, can also clearly find the deformation of the face contour phenomenon. Aspheric lens can not only reduce the thickness of the center and edge of the lens, but also make the lens thinner and eliminate peripheral aberration, thus giving the wearer natural vision. For consumers with high vision degree, aspheric lens may be more suitable.
Compared with aspheric surface, aspheric lens of the same material and degree is flatter, thinner, more realistic and more natural and comfortable. If you look at the lamp tube to see the shape of lens coating film, generally aspheric lens reflection tube is straighter (except for high-diopter lens); Due to the different curvature of the surface of spherical lens, the shape of lamp tube is more curved.