200 years of lighthouse lenses
This year we celebrate 200 years since the first lighthouse lens was put into operation. It was inserted into the iconic Le Cordouan lighthouse in France in 1823.
As early as the 18th century, experiments were carried out to concentrate and amplify the lighthouse beam with the help of mirrors and reflectors. The combination of oil burners, parabolic reflectors and mirrors was tested in several countries, but it was the Frenchman Augustin Fresnel (1788 – 1827) who was responsible for the greatest invention in the history of lighthouse technology. He constructed a lens device that combines focusing, refraction and reflection. This means that the light from the light source is collected in concentrated parallel "beam bundles" and very little of the light energy is wasted.
The lighthouses are signposts along our long and weather-exposed coastline. Lighting candles to guide seafarers has roots far back in history. The oldest sources that mention lighthouses are more than a thousand years old. The main challenge in the development of lighthouse technology has been to produce the strongest possible light at the lowest possible price. Another challenge was the wish to make the individual lighthouses recognizable.
The function of lighthouses is not only to warn ships when they are approaching the coast, they are also intended to indicate where on the coast you are. This requires that each lighthouse sends out a separate, identifiable light signal that the ships navigator can find on the sea chart. Various technical solutions have been developed to divide the light into different grades of light, including slats that rotate around the light source, "blinds" that open and close using a clockwork mechanism, or Dalén's device, where different sizes of the pressure valve make it possible to vary the speed of the light flashes from lighthouse to lighthouse.
From the middle of the 19th century, it was possible to construct lighthouse lenses which could rotate. This gave a far greater opportunity to vary the light character and create different frequencies of flashes, depending on the lens construction and rotation speed.
These inventions made it possible to develop a lighthouse technology where not only the large coastal lighthouses, but also every smallest lighthouse along the ship channel has its own identity and recognisability. The further development in the 20th century has mainly been about the transition to electricity as an energy source and the development of solar cell technology and LED lighting.
This exhibition is organized by Kystverkmusea and is produced by the Nordkappmuseet under its curator Emma Gunnarsson.
Kystverkmusea is the Norwegian Coastal Administration's official museum and was established in 2008. The museum is organized as a network collaboration between the Lindesnes Lighthouse Museum, Jærmuseet, VITI, Museum Nord and the Museums for coastal culture and reconstruction in Finnmark.