Plano-convex lens is a kind of positive lens. Its main functions in the optical system are beam expansion, imaging, beam collimation, focusing collimation, beam collimation point light source and other purposes. To reduce spherical aberration, when a plano-convex lens is used for focusing a collimated beam, the beam should be incident on the curved surface of the lens; when it is used for collimating a point light source, the beam should be incident on a plane. Plano-convex lenses have a positive focal length and are often used in applications such as imaging or beam collimation. Coated lenses are also widely used in visible light and near-infrared applications.