|a lens consisting of a number of smaller lenses arranged to give a flat surface of short focal length|
|[C20: named after Augustin Jean Fresnel (1788--1827), French physicist]|
|Fresnel lens (frə-něl') Pronunciation Key
A thin optical lens consisting of concentric rings of segmental lenses and having a short focal length. Placing a light source at the focal point of the lens gives rise to a strong beam of nearly parallel rays. Fresnel lenses are used primarily in spotlights, lighthouses, and the headlights of motor vehicles.