If you’ve been a hacker reader, you probably know what a fresnel lens is. You’ll find them in everything from overhead projectors to VR headsets. While this may seem commonplace now, the Fresnel lens was an important invention for its day because it revolutionized marine navigation, and according to a post on IEEE Spectrum, it was the driving force behind its invention. In fact, the lens has been called the “one million ship-saving invention.”
Arising from the problem on the problem. Navigating by the sun and stars is good, but it doesn’t work when you have a heavy cloud cover or if for some other reason you can’t see them. A lighthouse often marks an important point towards which you are or sometimes want to go away Of course, today we have GPS, but for a long time, a lighthouse was your best bet.
The problem is that in those days, a lighthouse had an oil lamp, a concave mirror and a simple lens. This made it difficult to identify the lighthouses. Napoleon started the lighthouse commission as part of the bridge and street corps. The optical talent employed by this corps was Augustine-Jean Fresnel. Although some lighthouses were already using lenses, they were not using special Fresnel-style lenses. There was speculation about such lenses, but Fresnel was not aware of them when he proposed his lenses for lighthouse use in 1819. His proposed lens was also a bit different than the previous ones.
The lenses act like a series of prisms, the edges of the edges bend the light more sharply and the center does not bend it at all. Compared to a conventional lens, a fresnel will be thinner and lighter or – conversely – for the same thickness and weight, the fresnel may have better properties. However, distortions make them less suitable for imaging where regular lenses still reign supreme. A thin lens, of course, has to go through more light, which is important when you are trying to shoot a ray over a long distance. Fresnel’s lenses allow 98% of the lamp’s output to pass through, which can signal ships up to 32 km away.
By 1823, lenses had appeared in lighthouses. By 1860, all lighthouses in the United States were using advanced optics. One of the things you don’t really care about is the fact that at one time it was a major technology. You have to wonder in 200 years what we are using today that will be left to the common and the common.
You can see the replica lighthouse lens in the video below. If you make your own, be careful not to have a big head.