Reaching Anew: The Story of the First Laptop

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In 1822, French civil engineer Augustin-Jean Fresnel (pronounced “Frey Nel”) invented a new type of lens that produced a much more powerful beam of light. The Fresnel lens is still used today in active lighthouses around the world. It is also found in movie projectors, magnifying glasses, spacecraft, and other applications.

Fresnel’s technical achievement deserves to be named an IEEE Milestone, according to the IEEE History Center, but no one has proposed it yet. Any IEEE member can submit a milestone proposal to the IEEE History Center. The Milestone program honors significant achievements in the history of electrical and electronics engineering.

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Due to growing complaints from French fishermen and ship captains about the poor quality of light emanating from lighthouses, the French Lighthouse Commission in 1811 set up a committee under the Corps des Ponts et Chaussées to study how the Headlight illumination could be improved.

One of the members of this committee was Fresnel, who worked for the French civil service corps as an engineer. He had considerable expertise in optics and light waves. In fact, in 1817, he proved his wave theory – which asserted that the wave motion of light is transverse rather than longitudinal – to be correct. In transverse waves, a wave oscillates perpendicular to the direction of its travel. Longitudinal waves, like sound, oscillate in the same direction as the wave travels.

Fresnel’s analysis of contemporary headlight technology revealed that the lenses were so thick that only half of the light produced passed through.

He decided he could do better by using his wave theory. His design consisted of 24 glass prisms of various shapes and sizes arranged in concentric circles within a metal cage. The prisms, placed both in front and behind four oil lamps, replaced both the mirror and the glass lens of the previous method. The prisms at the edge of the circle refract light slightly more than those closer to the center, so the light rays all emerge in parallel. The design could concentrate nearly 98% of the rays generated by the lamps, producing a beam visible over 20 miles away.

Inside the Fresnel lens of Lindesnes lighthouse in southern Norway.DeAgostini/Getty Images

A clock mechanism, which had to be wound by hand every few hours, was used to rotate the metal frame around the lamps to produce unique light patterns for specific headlights. A lighthouse could flash regularly every 5 seconds, for example, or it could have a dark period of 10 seconds and a bright period of 3 seconds. Captains counted the number of flashes emitted by a lighthouse to calculate the position of their ships.

The lenses were available in several sizes, called orders. The largest order, the Hyper-Radial, had a diameter of 1,330 millimeters. The smallest, the eighth order, had a diameter of 75 ml and was found in lighthouses in bays and rivers.

In 1823, the committee of the French Lighthouse Commission approved the use of the Fresnel lens in all lighthouses in France. That same year, the first was installed at the Cordouan lighthouse in southwestern France. The lens was eventually adopted in other countries. By the 1860s, all lighthouses in the United States had a Fresnel lens, according to the Smithsonian Institution.

Fresnel continued to modify the lens for several years. His final design, which he completed in 1825, could rotate 360 ​​degrees and was the first so-called fixed/flashing lens. It produced a steady light followed by a bright flash followed by another steady light.

With the invention of modern navigational tools, the lighthouse has become largely obsolete for maritime safety. But the lens invented for him lives on in the side mirrors used on trucks, solar panels and photographic lighting equipment.

If you would like to submit a proposal, do so here. The History Center is funded by donations to the IEEE Foundation. To learn more about the history of lighthouse technology, visit the websites of the US National Park Service, the Ponce Inlet Lighthouse and Museum, and the American Physical Society.

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