Fresnel lens, Optics, Light, Illumination

Fresnel lens, succession of concentric rings, each consisting of an element of a simple lens, assembled in proper relationship on a flat surface to provide a short focal length. The Fresnel lens is used particularly in lighthouses and searchlights to concentrate the light into a relatively narrow

Fresnel Lens (U.S. National Park Service)

Fresnel Lens - an overview

Fresnel Lens: Most Up-to-Date Encyclopedia, News & Reviews

Fresnel lens, Optics, Light, Illumination

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How do Fresnel lenses work? - Explain that Stuff

Fresnel Lenses

Fresnel lenses, explained by RP; annular rings, performance, applications