Cylindrical lenses have a cylindrical surface. Unlike spherical lenses, spherical lenses have a symmetrical effect on incident light in two directions, while cylindrical lenses only affect incident light in one direction.

Cylindrical lenses are generally used to focus parallel or divergent light beams onto a line or to change the aspect ratio of an image. Cylindrical lenses are generally designed for applications that require one-dimensional shaping of the light source. They have two structures: flat-concave and flat-convex, both of which are used for diverging or converging light beams respectively. A plano-convex cylindrical lens focuses the incident light onto a line, with a positive focal length, and consists of a plane and a convex cylinder. A plano-concave cylindrical lens consists of a plane and a concave cylinder, and its focal length is negative.