A type of lens used for lighting, developed in the mid-to-late 1700s and credited to French physicist and engineer Augustin-Jean Fresnel. Originally, the ideal behind the Fresnel lens was to create a thinner, lighter lens for focusing the light from lighthouses over longer distances. The first one was installed in a lighthouse in 1823; its light could be seen for more than 20 miles. Fresnel lenses are also used in car headlights, aircraft lighting (both exterior and interior applications such as highly focused passenger reading lights), traffic lights, and recently, solar energy applications. Fresnel lenses are also used for magnification in video, television, and other applications
The idea behind a Fresnel lens is to curve and shape the lens into various zones, which provide both magnification and focusing. Much less glass or plastic is required compared to a standard thick optical lens making a Fresnel lens lighter and less expensive than a conventional convex lens.
As stage lights, Fresnels can provide a very bright, tightly focused beam for illuminating a specific stage area or performer. Many Fresnels intended for stage use allow the lamp to be moved in the fixture in relation to the lens, allowing the user to change the width/height of the beam. When focused wide, Fresnels provide a soft edged beam, making them useful for wash applications in addition to spotlight applications when tightly focused.