A type of composite compact lens developed by the French physicist Augustin-Jean Fresnel for use in lighthouses. The design allows the construction of lenses of large aperture and short focal length without the mass and volume of material that would be required by a conventional optical lens. Instead of the curved surface of a conventional lens the Fresnel lens consists of a series of concentric grooves that act as individual refracting surfaces, bending parallel light rays to a common focal length.