Hyperradiant 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 in.). 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 (infringing Wigham's patent).[2]
A quadriform system was used at Galley Head lighthouse, Co. Cork, which at over 1 million candlepower was the most powerful light in the world when installed in 1879.
The hyper-radial lens was made in 1885, by the F. Barbier Company in Paris as a test lens for the lighthouse illumination trials then going on at the South Foreland Lighthouse in the UK. Chance Brothers Glass Company made their first hyper-radial lens in 1887 in the UK.[1]
These lenses were originally named biform, and later triform and quadriform lenses, by Wigham. Thomas Stevenson used the term hyperradiant lens, and later they were renamed the hyper-radial lens by James Kenward of the Chance Brothers Glass Company.
The hyper-radial Fresnel lenses were the largest ever actually put into use and were installed in about two dozen major "landfall" beacons around the world. The recipients include Makapu'u Point lighthouse on Oahu Island in Hawaii, Cabo de São Vicente in Portugal, Manora Point in Karachi, Pakistan, the famous Bishop Rock off the coast of Cornwall (in the UK), Cabo de Santa Marta in Brazil and Cape Race, Newfoundland.[1] By the 1920s, high-intensity lamp technology had rendered lenses of this size obsolete.
Footnotes
- 1 2 3 "Hyper-Radial Lenses". United States Lighthouse Society. Retrieved 2 February 2016.
- ↑ "John Richardson Wigham 1829–1906" (PDF). BEAM. Commissioners of Irish Lights. 35: 21–22. 2006. Archived from the original (PDF) on 12 March 2012.
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