Fresnel lenses

Invented by Augustin Fresnel, a French physicist who is considered to be the father of modern optics. These lenses are constructed in circular sections that allow a higher concentration of light (for example in lighthouse beacons) while also permitting a great reduction in the amount and weight of glass needed, relative to the amount required in the normal casting process for glass lenses.

(1) cross-section of a Fresnel lens (2) cross-section of a plano-convex lens of equivalent focal distance