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A Fresnel lens (pronounced or ) is a type of compact lens originally developed by French physicist Augustin-Jean Fresnel for lighthouses.〔(【引用サイトリンク】title=Fresnel lens )〕 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 lens of conventional design. A Fresnel lens can be made much thinner than a comparable conventional lens, in some cases taking the form of a flat sheet. A Fresnel lens can capture more oblique light from a light source, thus allowing the light from a lighthouse equipped with one to be visible over greater distances. ==History== The idea of creating a thinner, lighter lens by making it with separate sections mounted in a frame is often attributed to Georges-Louis Leclerc, Comte de Buffon. The marquis de Condorcet (1743–1794) proposed grinding such a lens from a single thin piece of glass. French physicist and engineer Augustin-Jean Fresnel is most often given credit for the development of the multi-part lens for use in lighthouses. According to ''Smithsonian'' magazine, the first Fresnel lens was used in 1823 in the Cordouan lighthouse at the mouth of the Gironde estuary; its light could be seen from more than out.〔Watson, Bruce. ("Science Makes a Better Lighthouse Lens." ) ''Smithsonian''. August 1999 v30 i5 p30. produced in ''Biography Resource Center''. Farmington Hills, Mich.: Thomson Gale. 2005.〕 Scottish physicist Sir David Brewster is credited with convincing the United Kingdom to adopt these lenses in their lighthouses.〔("Brewster, Sir David." ) ''Encyclopædia Britannica''. 2005. Encyclopædia Britannica Online. 11 November 2005.〕〔("David Brewster." ) ''World of Invention'', 2nd ed. Gale Group, 1999. Reproduced in ''Biography Resource Center''. Farmington Hills, Mich.: Thomson Gale. 2005.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「fresnel lens」の詳細全文を読む スポンサード リンク
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