The lenses are classified by the curvature of two optical surfaces. If one of the surfaces is flat and other is convex, the lens is plano-convex. Plano convex lens is the most common type of lens element. It is used to focus, collect and collimate light. In addition, Plano convex lens is also very useful as a simple imaging lens where image quality requirement is not too critical. For higher quality standards, these lenses are developed to ascertain tighter manufacturing tolerances.