Fresnel Lens


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Fresnel lens

[frā′nel ′lenz]
(optics)
A thin lens constructed with stepped setbacks so as to have the optical properties of a much thicker lens.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Fresnel Lens

 

a complex compound lens used in lighthouse and signal beacons. It was proposed by A. J. Fresnel. The lens does not consist of a single polished piece of glass with spherical or other surfaces like conventional lenses but instead is made of a

Figure 1. Cross section of ring-type Fresnel lens. In the center are rings whose outer surfaces are parts of toroidal surfaces. Along the edges of the lens are rings in which full internal reflection occurs in addition to refraction.

succession of individual, thin concentric rings, which in cross section have the shape of a special type of prism (see Figure 1). Such a design gives the Fresnel lens very low thickness, and therefore also very low mass, even for a large coverage angle. The sections of the rings are such that the spherical aberration of the Fresnel lens is slight and beams of light from point source S placed in the focus of the lens emerge, after refraction in the rings, in a practically parallel beam (in ring-type Fresnel lenses).

There are two types of Fresnel lenses: ring and belt. The ring-type (circular) lens is the system obtained by rotating the type shown in Figure 1 around optical axis SO; these lenses direct the stream of light in one particular direction. Belt-type (cylindrical) Fresnel lenses are obtained by rotating the type shown in Figure 1 around axis ASA’, perpendicular to SO; they propagate light from the source in all horizontal directions. The diameters of Fresnel lenses range from 10–20 cm to several meters.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

Fresnel lens

Fresnellens
In lighting, a lens that concentrates light from a small source such as an incandescent filament; similar to but thinner and lighter than a plano-convex lens owing to steps on the convex side; used in many types of luminaires, esp. downlights and spotlights.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.
References in periodicals archive ?
Yoshida et al., "Solar-pumped 80 W laser irradiated by a Fresnel lens," Optics Letters, vol.
"We're trying to determine whether the mariner could survive without that aid." Maines' organization helped relight the Yaquina Head lighthouse in 1997 after the cost of maintaining the Fresnel lens had grown too prohibitive for the government.
Basically, it was found that the solar light concentrating effect of Fresnel lens for IPCC reactor could result in an increase of 1.89~3.76 times of solar light irradiation ([UV.sub.a+b]) (Table 3), which is higher than that (1.2 times) of CPC reactor [15], and a raising heat irradiation in terms of 8~16[degrees]C increase of wastewater temperature in this study.
It is hard to measure the sun heat power because the power gain from the sun by Fresnel lens will cause very high temperature at focus.
The Holland building was painted a light yellow to match the existing steel beacon light, which received a larger, fourth-order Fresnel lens. Keeper Van Regenmorter, by then 70 years old, decided to retire rather than wrestle with all the newfangled equipment.
Hold up the Fresnel lens in front of your face and move it back and forth to enable the children to see the magnifying effect (e.g., on your nose, eyes, ears).
The extinction light variation is produced by an infrared light emitter with its associated Fresnel lens and a receiver (top-bottom in Figure 1).
In another example of how a package's decoration may affect sales, Sensodyne toothpaste created new cartons featuring WFT's Fresnel Lens film, and the brand moved up from the second best-selling brand for sensitive teeth to the top seller in Europe, according to Petersen.
Figure 3 represents the light path diagram for a Fresnel lens which has a flat surface and an uneven surface composed by several triangular teeth.
One low-cost solution uses a Fresnel lens with a narrow vertical-detection area that detects tall moving objects (humans).
Deployed on all carriers by 2004, IFLOLS--the improved Fresnel lens optical landing system--is a stack of 12 light cells, which produce a single ball-shaped image used by carrier pilots to determine the glideslope as they approach the carrier to land.
The fact that it was a Fresnel lens, made out of many concentric rings of glass fit together with a microscopic amount of space between them, meant that a specialist had to be employed to make sure the lenses were workable and accurate.