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A Fresnel lens (/ ˈ f r eɪ n ɛ l,-n əl / FRAY-nel, -nəl; / ˈ f r ɛ n ɛ l,-əl / FREN-el, -əl; or / f r eɪ ˈ n ɛ l / fray-NEL [1]) is a type of composite compact lens which reduces the amount of material required compared to a conventional lens by dividing the lens into a set of concentric annular sections.
The lighthouse was lit in 1908 with a temporary light. In 1910, a second-order Fresnel made by Barbier, Benard & Turenne [7] was purchased and installed. The lens floated in a mercury bath to provide very low turning friction. These massive lenses are 81.46 inches (2,069 mm) high, with a focal length of 27.6 inches (700 mm).
Barbier, Benard, et Turenne (BBT) was a French company founded in 1862, specializing in the manufacture of spotlights, Fresnel lenses for lighthouses, and lighting systems. [1] It was the world's leading producer of lighthouse beacons from the end of the 19th century onwards. It dissolved in 1982. [2]
With a final cost of $300,000, it was the most expensive light house that was ever constructed in the United States to that date. The lighthouse is built of large and heavy dovetailed granite blocks, which were cut and dressed ashore in Quincy and taken to the ledge by ship. The lighthouse was equipped with a third-order Fresnel lens.
Hyper-radial or hyperradiant Fresnel lenses are Fresnel lenses used in lighthouses. They are larger than "first-order" lenses , having a focal length (radius) of 1330 mm (52.36 inches). The idea was mentioned by Thomas Stevenson in 1869 [ 1 ] and first proposed by John Richardson Wigham in 1872, and again proposed by Thomas Stevenson in 1885 ...
Both the Cape Charles light and the Hog Island Light were electrified in 1933, completing the electrification of all coastal beacons in the fifth lighthouse district. In 1963 the lighthouse was fully automated and the first order Fresnel Lens was replaced by a more powerful DCB-224 aerobeacon.