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Topic: Fresnel lens

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	Fresnel Lens Discussion (Site not responding. Last check: 2007-10-14)
		It was a marvel....a complex array of dazzling glass prisms and bull's-eye lens mounted in a gleaming brass framework.
		To create the flash pattern, multiple lens panels were mounted around the cirumference of the Fresnel lens assembly which was mounted on wheels on a circular track or floated in container of mercury, reducing rotational friction to a minimum, and rotated at a precise rate controlled by a clockwork mechanism.
		They are used in the lens of traffic signals and to shape the light beam in overhead projectors as well as in molded plastic versions which are sometimes placed on the rear windows of motorhomes to broaden the drivers rearward field of view.
	www.lanternroom.com /misc/freslens.htm (895 words)

	The Fresnel Lens - LongIslandLighthouses.com
		Fresnel was the first person to demonstrate that two beams of light polarized in different planes do not exhibit interference effects and, from this experiment, theorized that light waves are transverse, rather than longitudinal (like that of sound).
		Fresnel's scientific work was known only to a small group of scientists during his lifetime, and some of his papers were not published until after his death.
		The single, nonrevolving lens, which is the same type of lens one sees on many 19th century hand-held lanterns, sends a steady beam in all directions unless the lamp inside employs some sort of rotating shutters, either solid or colored glass, which cause a flashing effect to the observer.
	www.longislandlighthouses.com /fresnel.htm (1247 words)

	Fresnel Lens (Site not responding. Last check: 2007-10-14)
		Faced with the need to construct a large lens for a lighthouse of appropriate focal length, but unable to support the large weight of a double convex lens of that size, French physicist Augustin Fresnel (1788-1827) reasoned that it was the surface curvature which gave the focusing power.
		The lens strength in diopters is defined as the inverse of the focal length in meters.
		The principal focal length of a lens is determined by the index of refraction of the glass, the radii of curvature of the surfaces, and the medium in which the lens resides.
	hyperphysics.phy-astr.gsu.edu /hbase/geoopt/fresnellens.html (183 words)

	Fresnel Lens (Site not responding. Last check: 2007-10-14)
		The Fresnel lens is clamped to the lens side of the ground glass with the ringed side of the Fresnel touching the ground side of the ground glass.
		Since the focal length of the fresnel should be such as to approximately match the distance of the exit pupil of the lens from the ground glass a Fresnel lens which works OK with "normal" focal length lenses may not work with wide angle or telephoto types.
		Since the focal length of the usual fresnel lens is intended for "normal" or somewhat long lenses, it doesn't correct for the effect of the wide angle lens, and, in fact, tends to focus the light too close to the ground glass.
	medfmt.8k.com /bronfresnel.html (15602 words)

	History of Admiralty Head Lighthouse - The Fresnel Lens
		Fresnel lenses are comprised of many smaller prisms, individually crafted and suspended in a complex arrangement.
		For the early lighthouse keepers, cleaning the lens and lantern house was a constant and important chore.
		When burners were removed and electric bulbs installed, a fourth order lens such as the one on display at Admiralty Head used about a 500-watt bulb, probably of a cylindrical design, rather than spherical, with the bulb placed with its axis in the vertical.
	www.admiraltyhead.wsu.edu /history/fresnel.html (724 words)

	The Fresnel Lens
		The developer of the lens was an obscure French physicist, Augustine-Jean Fresnel (pronounced "Fraynel"), born in 1788.
		Fresnel’s lens was readily adopted in Europe, but was late coming to America because of resistance by the Lighthouse Service.
		Fresnel lenses are extremely valuable, almost impossible to replace or repair, and their cleaning and maintenance are very labor intensive.
	home.maine.rr.com /springptlite/fresnel_lens.htm (365 words)

	LighthouseRatings.com - The Fresnel Lens Museum
		Fresnel's invention, known today as the Fresnel lens, created a way where only 17% of a light source would be lost.
		The first-order Fresnel lens was the largest of the Fresnel lenses and could exceed 12 feet in height and one ton in weight.
		The smaller Fresnel lens orders, the fourth through sixth orders, were often situated on lakes and harbors because of their limited nature of lens signal and visibility.
	www.lighthouseratings.com /Lens (615 words)

	Fresnel - Display Vocabulary for RDF - User Manual (Site not responding. Last check: 2007-10-14)
		Fresnel is a simple, browser-independent vocabulary for specifying how to display an RDF model [1] and how to style it using existing style languages such as CSS [2].
		Fresnel formats determine how the selected properties are rendered by specifying RDF-specific formatting attributes and by providing hooks to CSS [2], which is used to specify fonts, colors, margins, borders, and other decorative elements.
		Fresnel expresses RDF presentation knowledge in a declarative way; Fresnel applications should take all formatting information into account, but are free to interpret and adapt them in a way that is appropriate w.r.t their fundamental representation paradigm (e.g.
	www.w3.org /2005/04/fresnel-info/manual (6575 words)

	Fresnel Lens and Laser
		Mount the fresnel lens on a table, clip two large binder clips to the bottom of the lens, then place the lens so that it is perpendicular to the table.
		The farther from the lens the screen is placed the less the beam moves side to side until, at one distance, the beam moves very little.
		A point on the fresnel lens will always deflect initial direction of the laser beam (dashed line) toward the axis of the lens by the same angle, regardless of the angle with which the light hits the lens.
	www.exo.net /~pauld/activities/Fresnel_Lens_and_Laser.html (883 words)

	3Dlens.com - Fresnel Lens,Polarizer Fresnel Lens,Polarizer
		The Fresnel lens was invented by French physicist Augustine Fresnel, the Augustin Fresnel first used this lens design to build a glass Fresnel lens - lighthouse lens in 1822.
		The Fresnel lens is a thin, flat optical lens which consists of a series of small narrow concentric grooves on the surface of a lightweight plastic sheet in order to reduce the thickness, weight and cost.
		Fresnel lense can be designed and manufactured in very large sizes with light weight due to less than 4mm thickness, so the cost will be lower than traditional magnifiers.
	www.3dlens.com (654 words)

	Fresnel Lens
		Fresnel (born May 10, 1788, died July 14, 1827), a French physicist, was commissioned by France in 1822 to develop a better lighting system for the French lighthouses.
		Fresnel's task was to find the most efficient method to direct all, or nearly all, of the lamp's light rays out to sea.
		In addition, a Fresnel lens could be disassembled and shipped in sections and configured into virtually limitless numbers of light characteristics, that is, patterns of flashes of light divided by periods of darkness.
	www.parks.ca.gov /?page_id=22009 (347 words)

	Instructions for: Fresnel Lens (Site not responding. Last check: 2007-10-14)
		The modern version of Fresnel’s Lens is made of a thin sheet of plastic, with the prisms molded into one surface.
		A Fresnel Lens has the same curvature as a normal lens (as light is bent only at the interface between lens and air).
		The Fresnel Lens included in the Zoo is a converging lens, meaning that it focuses light rays inward along a central axis (which points perpendicular to the surface of the lens, away from the central point of the prism array).
	www.pa.uky.edu /sciworks/physicspettingzoo/Fresnel.htm (256 words)

	Fresnel lantern - Wikipedia, the free encyclopedia
		A Fresnel lantern (or merely Fresnel) is a spotlight used in theatre, which employs a Fresnel lens to wash light over an area of the stage.
		Theatrical Fresnels are typically made in 8, 6 or 3 inch varieties, referring to the diameter of the lens, with lamps ranging in wattage from 150w (typically with a 3-inch fresnel) to 2000w (with an 8-inch fresnel).
		Fresnels use a spherical reflector, with the filament of the lamp at the focus point of the reflector.
	en.wikipedia.org /wiki/Fresnel_lantern (720 words)

	Howstuffworks "How does a Fresnel lens work?"
		Fresnel studied light and optics in the 19th century.
		Fresnel lenses we first used in the 1800s as the lens that focuses the beam in lighthouse lamps.
		Large Fresnel lenses are often used as solar concentrators.
	www.howstuffworks.com /question244.htm (352 words)

	Boston Light Fresnel Lens
		The Fresnel Lens was in use in Europe for 20 years before it came to America.
		In 1841, the first Fresnel Lens was installed at Navesink Lighthouse, NJ, and in 1852 the Lighthouse Board was created.
		The Coast Guard still maintains the priceless Fresnel Lens, just as their predecessors did, but with one advantage: they no longer have to extinguish it at dawn and relight it at dusk.
	www.harbourlights.com /catalog/2003/hl_boston_lens.htm (421 words)

	Fresnel Lenses
		The lens could be as tall as twelve feet high with concentric rings of glass prisms above and below a center drum section to bend the light into a narrow beam.
		Smaller Fresnel lenses, such as the sixth-order lens, were installed in smaller lighthouses, such as breakwater lighthouses.
		This Third and a Half Order lens was one typically built for service on the Great Lakes as it was a medium size between a Fourth and Third Order lens, a Fourth was to small and a Third was just to large for the intended use.
	www.michiganlights.com /fresnel.htm (1010 words)

	Large-Aperture Fresnel Lenses
		Fresnel lenses are the diffractive equivalents of a refractive lens.
		The quadratic phase profile of a lens is quantized to a one-wave deep kinoform profile.
		Fresnel lenses offer advantages of being able to be fabricated on thin, lightweight substrate while maintaining high diffraction efficiency and excellent optical quality.
	www.llnl.gov /nif/psa/diffractive-optics/fresnel.html (154 words)

	Edmund Optics - Aspherically Contoured Fresnel Lenses
		A Fresnel lens replaces the curved surface of a conventional lens with a series of concentric grooves, molded into the surface of a thin, lightweight plastic sheet.
		Fresnel lenses are most often used in light gathering applications, such as condenser systems or emitter/detector setups.
		Fresnel lenses can also be used as magnifiers or projection lenses; however, due to the high level of distortion, this is not recommended.
	www.edmundoptics.com /IOD/DisplayProduct.cfm?productid=2039 (234 words)

	The Fresnel Lens (Site not responding. Last check: 2007-10-14)
		The lens could be as tall as twelve feet, with concentric rings of glass prisms above and below to bend the light into a narrow beam.
		Tests showed that while an open flame lost nearly 97% of its light, and a flame with reflectors behind it still lost 83% of its light, the fresnel lens was able to capture all but 17% of its light.
		First, the lens is formed into round "bull's eyes" which bend the light into a beam rather than a flat sheet.
	lighthousegetaway.com /lights/fresnel.html (381 words)

	Planning the Fresnel Lens Exhibit
		The Hog Island Lens exhibit was accomplished in two phases in 2002 and 2003, after the lens sat in storage for over 30 years in a Portsmouth, VA city warehouse.
		Prior to the tower's demise, in 1941, the lens was removed from the Hog Island Lighthouse (without its pedestal and rotating assembly) and loaned to the Mariner's Museum in Newport News, VA, where it was placed on exhibit.
		In 1964 the lens exhibit was replaced with the Cape Charles first-order lens, which was complete with its rotating assembly, and the Hog Island lens was transferred to the City of Portsmouth.
	www.hnsa.org /conf2004/papers/dunlap.htm (1337 words)

	Applications of the Fresnel Lens
		The Fresnel lens (often pronounced FREZ-nell but usually the original fre-NELL in theatrical and motion picture lighting applications) reduces the amount of material required compared to a conventional spherical lens by breaking the lens into a set of concentric annular sections known as Fresnel zones.
		For the reasons given above, Fresnel lenses tend to be used in applications where weight of the lens is at a premium and/or image quality is unimportant.
		Fresnel lenses for lighthouses are classified in six orders based on the focal length of the lens.
	www.edinformatics.com /inventions_inventors/fresnel_lens.htm (364 words)

	Fresnel Technologies, Inc. - Precision Diamond Machined and Molded Optics
		Fresnel Technologies, Inc., founded in 1986, is a leading manufacturer of molded plastics Fresnel lenses and related optical components.
		Specialties within these areas include Fresnel lens arrays for passive infrared (PIR) motion sensing, diffusers and microlens arrays for illumination, and plastics Fresnel lenses for use in environmental monitoring near 3.4 micrometers.
		Each groove of the Fresnel lens is a small piece of the aspheric surface, translated toward the plano side of the lens.
	www.fresneltech.com (390 words)

	Fresnel lens - Wikipedia, the free encyclopedia
		A Fresnel lens is a type of lens invented by Augustin-Jean Fresnel (pronounced fre-NELL in scientific and lighting applications, although often pronounced FREZ-nell).
		Compared to earlier lenses, the Fresnel lens is much thinner, thus passing more light and allowing lighthouses to be visible over much longer distances.
		In the Terry Gilliam film Brazil (film), plastic fresnel screens appear obstenibly as magnifiers for the small CRT monitors used throughout the offices of the Ministry of Information.
	en.wikipedia.org /wiki/Fresnel_lens (1073 words)

	Fresnel Lens
		The lantern house was surrounded a central bull's-eye lens with a series of concentricglass prismatic rings.
		By adding triangular prism sections above and below the main lens, it steepened the angle of incidence at which rays shining up and down (lost light) could be collected and made to emerge horizontally.
		Fresnel designed different size apparatus for different requirements for different lighthouses.
	www.capemeareslighthouse.org /Fresnel_Lens/fresnel_lens.html (135 words)

	Seguin Island Lighthouse- The Light
		Invented by a French physicist, Augustine Jean Fresnel, (pronounced fruh-nel) the concept was to capture as much light as possible from a source (the lamp) and, with the use of prisms, redirect it into a concentrated beam.
		The first use of the Fresnel Lens was in France in 1822.
		In 1857 a First Order Fresnel Lens was installed at Seguin Island which greatly increased the visibility of the light.
	www.seguinisland.org /seguin_fresnel_page.htm (456 words)

	Fresnel Lens
		We did not have the lens for too long before we were all seeing spots and heading to the nearest welding supply shop.
		Thus Dr. Chris now owns the lens and (for obvious reasons) it is kept at least 1000 miles away from him at all times.
		The lens was somewhat flexible so the corners didn't tend to contribute much.
	www-personal.umich.edu /~bclee/lens.html (1136 words)

	AUGUSTINE FRESNEL INVENTOR OF THE LIGHTHOUSE FRESNEL LENS SYSTEM \| HOW THINGS WORK
		A fresnel lens looks like a giant glass beehive, with a light at the center.
		The lens could be (and usually is) as tall as twelve feet, with concentric rings of glass prisms above and below to bend the light into a narrow beam.
		Because of the improved range, it became necessary to build taller light houses to enable the full range to be achieved - hence overcome the curvature of the earth.
	www.solarnavigator.net /history/fresnel_lens.htm (696 words)

	PiN Submodule: Fresnel Lens
		In fact, only the outer surface of the lens is needed.
		Later, Augustin Fresnel modified this idea and the modern Fresnel lens was created.
		His lenses were first used on the French coast as a lightweight and less-expensive alternative to the old, bulky lighthouse lenses.
	acept.la.asu.edu /PiN/mod/light/supp/fresnel.html (213 words)

	Fresnel Lens Systems - Reflexite Display Optics - Rui Fei Optics, projector lenses
		Fresnel Optics is a Rochester based manufacturing company, which develops, manufactures and markets microstructured optical components for the display industry, digital projection industry, lighting industry and photographic marketplace.
		The Rui Fei factory will produce optical components such as Fresnel lens systems for overhead projectors, primarily for the Asian market.
		Chen, who has managed the facility for the past five years, holds both BS and MS degrees in Mechanical Engineering and Hydraulics, and reports directly to Dr. Foley.
	www.fresneloptics.com /about_news_october2000.htm (378 words)

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