Fresnel lens
A Fresnel lens is an optical lens, which was originally developed for Lighthouses. It is named after its inventor, French physicist Augustin-Jean Fresnel. The name is pronounced /freɪˈnɛl/ (fray-NELL), the 's' is silent. Before Fresnel, Buffon and Condorcet proposed a similar design, as a way to make large burning lenses.
The design allows the construction of lenses of large aperture and short focal length without the weight and volume of material that would be required in conventional lens design. Compared to earlier lenses, the Fresnel lens is much thinner. More light can pass through. Lighthouses that use these kind of lenses can be seen from farther away.
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Fresnel Lens Media
First-order group-flashing Fresnel lens, on display at the Point Arena Lighthouse Museum, Point Arena Lighthouse, Mendocino County, California. The three dioptric panels (inside the brass rings) and three catadioptric panels (outside) are partly split in two, giving three double-flashes per rotation.
1: Cross-section of Buffon/Fresnel lens. 2: Cross-section of conventional plano-convex lens of equivalent power. (Buffon's version was biconvex.)
Description of lens orders, from Block Island Southeast Light, Rhode Island.
- Makapuupointlight
Inchkeith lighthouse lens and drive mechanism
1956 Bel Air, with Fresnel lenses in round headlamp and rectangular marker lamp
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