Augustin-Jean Fresnel


I had the good fortune to serve as a lighthouse docent a few years ago at Cape Blanco Lighthouse on the coast of Oregon. As someone interested in lighting (!) I was awed by the beautiful, sculpture like, Fresnel lens that sent a beam of light 23 miles across the Pacific ocean while powered by a mere150 watt halogen bulb. First developed in the 1820's by Augustin-Jean Fresnel, a French physicist, has been called "the invention that saved a million ships."

Augustin-Jean Fresnel

Augustin-Jean Fresnel (fray-NEL) is an idol of mine. He was a French civil engineer and physicist who invented the remarkable Fresnel Lens in the 1820's, which has been used in lighthouses around the world ever since.

He's the inspiration behind Audette Collection. We believe that automotive lighting is a science and a critical safety factor, and shouldn't be left to chance or flashy marketing. That's why we strive to offer only Best in Class® products.

Fresnel’s system was based on a key principle of geometric optics: when light passes from one medium to another – for example, air to glass and then to air once again – it changes direction. The lens’ concentric arrangement and ‘bending’ of light created a combined light intensity much greater than the light source itself. This in turn allowed the light to be visible over greater distances. Fresnel installed his invention at Cordouan, a lighthouse already prominent in his home country, in an area known for its rugged coastlines and treacherous swells. By the 1860s, thousands of lighthouses had been fitted with Fresnel lenses, from small harbour lanterns to great sea lights.

“Every lighthouse has its own signature,” said Mickael Neveu, one of four lighthouse guardians who live year-round at Cordouan (guardians take turns in pairs, for a fortnight at a time). He gestured towards the Fresnel apparatus inside the tower, which is restricted to keepers and custodians. “The light here occults three times every 12 seconds.”

An occulting light is a rhythmic light in which the duration of light in each period is longer than the total duration of darkness: in other words, it has the appearance of flashing off, rather than flashing on. As Cordouan’s lens rotates, its bulls-eye panels create beams of concentrated light, which successively pass into view of the mariner: to the south, a flash of red, to the west, green or white light, followed by darkness. These different colours direct maritime traffic according vessel size: the green sector indicates the main passage of the estuary, used by high-tonnage commercial shipping; the south passage, marked by the red sector, is used by vessels of shallower draught. 

Taken from BBC Travel






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