The Fresnel lens is almost the very first, according to historical chronology, a device based on the principle of light diffraction. Despite the age of this invention, it has not lost its relevance today and has found application in many areas.
What is Fresnel Lens
The Fresnel lens is called a complex composite lens. Unlike ordinary lenses, it does not consist of a single polished piece of glass with a spherical surface, but of individual concentric rings. They are tightly adjacent to each other and have a small thickness. In cross-section, they are prisms of a special profile. This type of lens got its name from the French physicist Augustin Fresnel, who proposed it, who worked in the field of physical optics.
Thanks to its unique design, this lens model is lightweight and lightweight. The sections of its rings are constructed in such a way that its spherical aberration is extremely small, as a result of which the rays refracted by it come out in a single parallel beam. The diameter of the Fresnel Lens varies from a couple of centimeters to several meters.
Fresnel lenses are usually subdivided into annular and belt lenses. The first ones direct a beam of light in some one, predetermined direction. The latter, on the other hand, send light from a source in all directions in one plane.
Fresnel Lens Applications
Today, the Fresnel lens has found wide application in many areas.
For example, they are used in large beacons, projection TVs, navigation lights, railway lens traffic lights, and semaphore lights. And due to its low weight, the Fresnel lens is also used in lighting devices that need to be moved during operation.
And when placed on the rear window of a car as a thin film, it significantly reduces the blind spot behind the car seen in the rearview mirror.
Based on the Fresnel lens, an ultra-flat lightweight magnifier is created. It is her help that people with low vision resort to when reading texts in small print.
In addition, these lenses are used in infrared motion sensors and lens antennas.
There are a couple more promising areas in which the use of the Fresnel lens is possible. Its use is presumably possible in the construction of space telescopes of gigantic diameters.
It is also likely to be used as a solar energy concentrator for solar panels.
For all its advantages, the Fresnel lens has one significant drawback - the presence of transitional edge sections causes a high proportion of parasitic illumination and "false images". This makes it impossible to use it in the construction of accurate optical images.
