Concept: A cylindrical lens is made from a section of a cylindrical glass, consisting of a cylinder and a plane, including flat-concave and flat-convex lenses.
Optical properties: Light rays passing through an axial meridian (the vertical direction in the figure) do not change in convergence and divergence. A change in convergence and divergence occurs when light passes through the meridian of refraction (the horizontal direction in the figure).
Applications: Cylindrical mirrors are generally used to focus incoming light onto a line, or to change the aspect ratio of an image. Cylindrical mirrors have a cylindrical surface that allows incident light to focus on a dimension and stretch the image. Cylindrical mirrors can have negative or positive focal length and are suitable for laser line generation or deformation beam shaping to cyclize laser output.