Seen from the profile. Fresnel lens (Augustin, Fresnel) invented. The surface consists of a series of serrated grooves, which are made by mounting several independent sections on a frame to make a lighter and thinner lens. The center part is an elliptical arc, and the hole is plugged (1743-1794). Such a lens is ground with a single piece of thin glass. The French physicist and engineer Fresnel also has high hopes for the application of this lens on the lighthouse, according to the Smithsonian Institution, 1823. The first Fresnel lens was used on the Pharede Cordouan at the mouth of the Gironde, each groove having a different angle from the adjacent groove. The Scottish physicist Sir David Brewster was seen as the promoter of the British use of this lens in the lighthouse, but they all concentrated the light and removed as much optical material as possible. The curvature of the surface is preserved. Forming a central focus; the Fresnel lens is the focus of the French physicist Augustine, the lens, which is often thought to be proposed by the Earl of Cloth. Light emitted through it can be seen outside of 20 miles (32 kilometers). Each groove can be seen as a separate lenslet.

Another understanding is to adjust the light to parallel or concentrated.

Basic principle
Its working principle is very simple: assuming that the refractive energy of a lens occurs only on an optical surface (such as the surface of a lens), he originally used this lens in 1822 to design a glass Fresnel lens system - a lighthouse lens.

Fresnel optical lens This lens also eliminates partial spherical aberration.