Aspheric lenses have surfaces which do not resemble segments of a sphere or cylinder. Instead, aspheric lenses have a profile that changes in curvature across the surface. This type of lens is designed to reduce spherical and optical abberrations without the need for a multi-lens assembly. Aspheric lenses are used for laser diode collimation and optical fiber coupling, but are also used in many eyeglasses and consumer electronics. Small glass and plastic aspheric lenses can be molded, but large glass lenses require grinding and polishing. Finishing techniques to reduce insertion loss and improve surface quality are common.