A type of instrument which produces an even, soft edged beam of light through a fresnel lens. the lens is a series of stepped concentric circles on the front and pebbled on the back and is named after its French inventor, Augustine Jean Fresnel ( 1788-1827). He developed the lens for french light houses so they can be seen further out to sea and could achieve a longer focal length with a lot less glass than a standard plano-convex lens
« Back to Glossary Index