from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A thin optical lens consisting of concentric rings of segmental lenses and having a short focal length, used primarily in spotlights, overhead projectors, and the headlights of motor vehicles.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. The hollow cylindrical lens used in the Fresnel lamp.
from the GNU version of the Collaborative International Dictionary of English
- See under lens.
- n. a compound lens formed by placing around a central convex lens rings of glass so curved as to have the same focus; used, especially in lighthouses, for concentrating light in a particular direction; -- so called from the inventor.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. lens composed of a number of small lenses arranged to make a lightweight lens of large diameter and short focal length
After Augustin Jean Fresnel.(American Heritage® Dictionary of the English Language, Fourth Edition)
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