Plano-convex lenses can focus a collimated beam at the back focus, or a point light source can be turned into a collimated beam. Jingsheng's plano-convex lenses are usually made of K9 glass, and their anti-reflection coating is aimed at the wavelength range of 400~700 nanometers. There are also UV quartz as the base material for processing. When UV quartz is used as the base material, it has good transmittance and low thermal expansion coefficient in the ultraviolet region, and can be plated with UV AR film for special circumstances.