9/21/12 - "1st Order Fresnel Lens"



1st Order Fresnel Lens


At the Fire Island Lighthouse in New York.

     "In 1822, a French physicist named Augustin Fresnel (pronounced: Fur-nel) designed an innovative lens system that would forever revolutionize the history of nautical navigation.
In that year, Fresnel put his design efforts toward finding a solution to how dispersed light could be captured, intensified, optimized and focused to a higher degree than contemporary means so it could serve lighthouses more efficiently.

      Prior to Fresnel's creation, lighthouses would burn sperm whale oil in lamps in their light towers. This system proved expensive and also inefficient, as the light generated by this method lost 97% of its generated light, since it would be dispersed in all directions and not necessarily focused in the direction pointing out to sea.

      As a slight improvement to this method, small mirror-like reflectors were installed behind the burning lamps to redirect the useless light escaping through the back of the tower. The reflectors redirected the back-escaping beam to the front of the tower, where it could then be used as part of the light signal to vessels on the water. These lamps consisted of variations called Argand lamps and then later Lewis lamps. Even with this improvement, using this method still lost about 40% of the dispersed light.
Fresnel's invention, known today as the Fresnel lens, created a way where only 17% of a light source would be lost. By creating a lens that completely surrounded the light source with concentric rings of glass prisms, Fresnel designed a way to take a dispersed light source heading in multiple directions and redirect it through collected prisms by bending and redirecting the light beams. This "bending" of the beams through a Fresnel lens pointed all of the light source in the same direction to create a very intense, focused and unified light beam that could be seen more than 20 miles out to sea using just a 1,000-watt light bulb!"


http://www.lighthouseratings.com/Lens/




Camera Data

Canon
Canon EOS 5D
1/99 second
F/5.6
47 mm
50
Aug 12, 2012, 11:04:16 AM
Adobe Photoshop CS Windows

Followers

Total Pageviews

Tweet