Fresnel lens

noun

Fres·​nel lens ˈfrez-nəl-  frā-ˈnel- 

: a lens that has a surface consisting of a concentric series of simple lens sections so that a thin lens with a short focal length and large diameter is possible and that is used especially for spotlights

Word History

Etymology

Augustin J. Fresnel

First Known Use

1865, in the meaning defined above