A Cylindrical lens is a special type of cylinder lens, and is highly polished on the circumference and ground on both ends. Cylindrical lenses perform in a manner analogous to a standard cylinder lens, and can be used in beam shaping and to focus collimated light into a line. Cylindrical lenses are optical lenses which are curved only in one direction. Therefore, they focus or defocus light only in one direction, for example in the horizontal direction but not in the vertical direction. As for ordinary lenses, their focusing or defocusing behavior can be characterized with a focal length or its inverse, the dioptric power. Cylindrical lenses can be used to obtain a beam focus of elliptical form. That can be required, for example, for feeding light through the entrance slit of a monochromator or into an acousto-optic deflector, or for conditioning pump light for a slab laser. There are fast axis collimators for diode bars, which are essentially cylindrical lenses – often with an aspheric shape. Cylindrical lenses cause astigmatism of a laser beam: a mismatch of focus position for both directions. Conversely, they can also used for compensating astigmatism of a beam or an optical system. For example, they may be required for collimating the output of a laser diode such that one obtains a circular non-astigmatic beam. The main significance of a cylindrical lens is its ability to focus light onto a continuous line rather than a fixed point. This quality gives the cylindrical lens various unique abilities, such as laser line generation. Some of these applications simply aren’t possible with a spherical lens. Cylindrical lens capabilities .