wordswarm.net: free dictionary lookup
Wordswarms From Years Past


13-Letter Words
12-Letter Words
11-Letter Words
10-Letter Words
9-Letter Words
8-Letter Words
7-Letter Words
6-Letter Words
5-Letter Words
4-Letter Words
3-Letter Words


Adjacent Words

Freshwater
freshwater bass
freshwater bream
freshwater clam
freshwater cordgrass
freshwater drum
freshwater eel
freshwater fish
freshwater limpet
freshwater mussel
freshwater pearl
Freshwatered
Fresnel
Fresnel lamp
Fresnel's rhomb
Fresno
fress
Fret
Fret saw
FRET, FRETTING
Freta
Fretful
Fretful-ly
Fretful-ness
Fretfully

Fresnel lens definitions

WordNet (r) 3.0 (2005)

n
1: lens composed of a number of small lenses arranged to make a lightweight lens of large diameter and short focal length

Merriam Webster's

noun Etymology: Augustin J. Fresnel Date: 1865 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

Britannica Concise

Series of concentric rings, each consisting of a thin part of a simple lens, assembled on a flat surface. G.-L.-L. Buffon (1748) first had the idea of dividing a lens surface into concentric rings to reduce the weight. In 1820 his idea was adopted by Augustin-Jean Fresnel (1788-1827) for the construction of lighthouse lenses. Fresnel lenses have the optical properties of much thicker and heavier lenses. They are used in spotlights, floodlights, railroad and traffic signals, and decorative lights. Some thin Fresnel lenses are molded in plastic, the width of the rings being only a few thousandths of an inch; such lenses are used in cameras and small projectors.

Webster's 1913 Dictionary

Lens Lens (l[e^]nz), n.; pl. Lenses (-[e^]z). [L. lens a lentil. So named from the resemblance in shape of a double convex lens to the seed of a lentil. Cf. Lentil.] (Opt.) A piece of glass, or other transparent substance, ground with two opposite regular surfaces, either both curved, or one curved and the other plane, and commonly used, either singly or combined, in optical instruments, for changing the direction of rays of light, and thus magnifying objects, or otherwise modifying vision. In practice, the curved surfaces are usually spherical, though rarely cylindrical, or of some other figure. Lenses Note: Of spherical lenses, there are six varieties, as shown in section in the figures herewith given: viz., a plano-concave; b double-concave; c plano-convex; d double-convex; e converging concavo-convex, or converging meniscus; f diverging concavo-convex, or diverging meniscus. Crossed lens (Opt.), a double-convex lens with one radius equal to six times the other. Crystalline lens. (Anat.) See Eye. Fresnel lens (Opt.), 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. Multiplying lens or glass (Opt.), a lens one side of which is plane and the other convex, but made up of a number of plane faces inclined to one another, each of which presents a separate image of the object viewed through it, so that the object is, as it were, multiplied. Polyzonal lens. See Polyzonal.

Webster's 1913 Dictionary

Fresnel lens Fres`nel" lens" [See Fresnel lamp.] (Optics) See under Lens.



Wordswarm.net: Look up a word or phrase

 


wordswarm.net: free dictionary lookup