Lenses are classified by the curvature of the two optical surfaces. A lens is biconvex if both surfaces are convex. If both surfaces have the same radius of curvature, the lens is equiconvex. If one of the surfaces is flat, and the other one of the surface is convex, the lens is plano-convex lens.

The plano convex lens is the most common type of lens element. It can be used to focus, collect, and collimate light. A plano convex lens is useful as a simple imaging lens for systems where image quality requirement is not too critical.