Fresnel Lens Museum
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!
Through the years seven classifications of Fresnel lenses were developed. These classifications, know as “orders,” were developed to meet all the needs of the many different lighthouses and the diverse coastal environment each lighthouse stood within.
The first-order Fresnel lens was the largest of the Fresnel lenses and could exceed 12 feet in height and one ton in weight. Because of their size and strength, these lenses primarily were used in lighthouses that needed an extremely focused and far-reaching signal. These lights were usually utilized in lighthouses along oceans.
The smaller Fresnel lens orders, the fourth through sixth orders, were often situated on lakes and harbors because of their limited nature of lens signal and visibility.
These lenses were also made to spin on a pedestal, placed in the light tower, so that the different spacing placement of the multiple bull’s-eyes on each lens would result in different intervals between their flashes – when the center of the bull’s-eye on the lens lined up with the ship out at sea viewing the light. These flashes happening in different intervals, which were unique to each lighthouse, helping those at sea easily identify which lighthouse they were viewing and where they were along a coastline.
Different-color lenses were also used, as well as different colored light sources, as a way to distinguish lighthouses from each other.
Today, most of the existing Fresnel lenses have been moved out of light towers and into museums to safeguard their preservation. Very few lighthouses in America still have a first-order Fresnel lens in their towers. Bodie Island Lighthouse, Block Island Southeast Light, St. Augustine Lighthouse, Cape Meares Lighthouse, Heceta Head Light, the new Cape Henry Lighthouse and Seguin Island Lighthouse are some of the few places in America where you can see a first-order Fresnel lens still in use.
Below are pictures of Fresnel lenses that have been collected for your enjoyment!