Fresnel Lens


Lighthouses were built along shorelines around the world for the single purpose of guiding travelers through the often dangerous and rough waters. Each lighthouse had its own unique structure. Each light signal identified the specific location for the travelers.

Many early lighthouses were lit with candles, oil lamps and, later, electricity. However, a better way to disperse the light in a wider, stronger beam was sorely needed. Around 1821, a young Frenchman by the name of Augustin Fresnel (pronounced “freh-nel”) invented a central lens surrounded by prisms, which dramatically increased the strength of the light source. Fresnel lenses were installed in lighthouses around the world, and still can be found in some lighthouses.

In its simplest form, the Fresnel Lens was a barrel-shaped array of lenses encircling the light source. As much as 80% of the light was captured by the lens and transmitted some 13 to 20 nautical miles out over the water from the top of the lighthouse tower.

There is a 4th Order Fresnel Lens on display at the Tom Ridge Environmental Center. It is not the lens from the Presque Isle Lighthouse. There is a 4th Order Lens, originally mounted in the North Pier Light, on display at the Erie Maritime Museum. The North Pier light is very similar to the one at PILH. There is also a Fresnel Lens on loan to the Presque Isle Lighthouse. You can observe it in the PILH Lake Room display. It is similar is size, not design.

TOP: Fourth Order Fresnel lens in the Lake Room, on loan. Portrait of Augustin Fresnel

MIDDLE: 6 10-watt donuts = 60 watts of illumination. Electronic eye turns on at dusk, off at dawn, and on during a daytime storm.

BOTTOM: Top of the Tower at 57′ 4″.