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The lantern house was surrounded a central bull's-eye lens with a series of concentricglass prismatic rings. By adding triangular prism sections above and below the main lens, it steepened the angle of incidence at which rays shining up and down (lost light) could be collected and made to emerge horizontally. All the collected light emerged through the bull's-eye as a narrow, horizontal pencil-like beam. This is known as the Fresnel catadioptric system.
Fresnel designed different size apparatus for different requirements for different lighthouses. They were designated First (1st) through Sixth (6th) Order and varied in size from 72 7/16 inches (1st Order) down to 11 3/16 inches (6th Order) inside diameter. Refer to our History page for additional information about the Cape Meares first order Fresnel lens.
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