Fresnel lighthouse lens
A lens of glass rings that gathered a lighthouse’s light into a beam visible miles out to sea.
The physicist Augustin Fresnel (1788–1827) showed his lens to the French Lighthouse Commission in 1822, and the first was installed at Cordouan in 1823. Such lenses were used in lighthouses all over the world. Examples are in the Musée national de la Marine and many lighthouse museums.
Materials: Ground crown glass in a brass frame
Manufacture: The lens was divided into concentric rings and prisms, ground separately and mounted in a brass cage.
The stepped glass rings instead of one thick lens.
The prisms at top and bottom that bend the light into the beam.