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	Fresnel zone - Wikipedia, the free encyclopedia
		In optics and radio communications, a Fresnel zone (pronounced as FRA-nel Zone), named for physicist Augustin-Jean Fresnel, is one of a (theoretically infinite) number of a concentric ellipsoids of revolution which define volumes in the radiation pattern of a (usually) circular aperture.
		The concept of Fresnel zones may also be used to analyze interference by obstacles near the path of a radio beam.
		For establishing Fresnel zones, we must first determine the RF Line of Sight (RF LoS), which in simple terms is a straight line between the transmitting and receiving antennas.
	en.wikipedia.org /wiki/Fresnel_zone (235 words)

	Fresnel lens - Wikipedia, the free encyclopedia
		Cheap Fresnel lenses can be stamped or moulded out of transparent plastic and are used in overhead projectors, projection televisions, and hand-held sheet magnifying glasses.
		Glass fresnel lenses also are used in lighting instruments for theater and motion pictures; such instruments are often called simply fresnels.
		Many fresnel instruments allow the lamp to be moved relative to the lens focal point, which creates a more or less hard-edged light beam.
	en.wikipedia.org /wiki/Fresnel_lens (472 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 (334 words)

	Seeing The Light - The Fresnel Lens
		Fresnel was a physicist who was well known for his experimentation with the theories of light reflection and refraction.
		With Fresnel's optic array, output was increased dramatically from the old reflector systems, with as much as eighty percent of the light transmitted over twenty miles out to sea.
		A Fresnel lens could be built in one location, disassembled and easily shipped in multiple small sections, making transportation and re-assembly in the tight confines of a lantern room significantly easier than would have been the case with an optic made up of few huge glass components.
	www.terrypepper.com /lights/closeups/illumination/fresnel/fresnel.htm (1073 words)

	Fresnel Lenses for Wide- Aperture Optical Receivers
		Plastic Fresnel lenses are commercially available in diameters up to 5 m — large enough to satisfy requirements for aperture widths of the order of meters for collecting sufficient light in typical long-distance free-space optical communication systems.
		Fresnel lenses are not yet suitable for high-quality diffraction- limited imaging, especially in polychromatic light.
		In that case (see figure), the light collected by each Fresnel lens could be collimated, the collimated beams from the four Fresnel lenses could be reflected onto a common off-axis paraboloidal reflector, and the paraboloidal reflector would focus the four beams onto a single photodetector.
	www.nasatech.com /Briefs/May04/NPO40436.html (472 words)

	Fresnel reflection - Wikipedia, the free encyclopedia
		In optics, Fresnel reflection is the reflection of a portion of incident light at a discrete interface between two media having different refractive indices.
		In general, the greater the angle of incidence with respect to the normal, the greater the Fresnel reflection coefficient, but for radiation that is linearly polarized in the plane of incidence, there is zero reflection at Brewster's angle.
		Antireflection coatings reduce overall Fresnel reflection by mutual interference of individual Fresnel reflections at the boundaries of the individual layers.
	www.wikipedia.org /wiki/Fresnel_reflection (236 words)

	The Fresnel Lens - LongIslandLighthouses.com
		Augustin Jean Fresnel (pronounced "Fruh-nel") (1788-1827), was a French physicist and an early adherent of the wave theory of light.
		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.
	www.longislandlighthouses.com /fresnel.htm (1255 words)

	Fresnel Lens (Site not responding. Last check: 2007-10-22)
		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)

	Fresnel equations - Wikipedia, the free encyclopedia
		The Fresnel equations, deduced by Augustin-Jean Fresnel, describe the behaviour of light when moving between media of differing refractive indices.
		The fraction of the intensity of incident light that is reflected from the interface is given by the reflection coefficient R, and the fraction refracted by the transmission coefficient T.
		The Fresnel equations may be used to calculate R and T in a given situation.
	www.wikipedia.org /wiki/Fresnel_equations (547 words)

	Fresnel (Site not responding. Last check: 2007-10-22)
		Fresnel began working on this project in 1812 when he was based in Nyon but already he was undertaking scientific work in his spare time.
		It was a great chance for Fresnel to put his revolutionary work before the world and he was very confident of his theory since his mathematical deductions from the one simple hypothesis led to results which he had verified experimentally giving a highly accurate agreement between theory and experimental evidence.
		Fresnel died of tuberculosis in 1827 at the age of 39.
	www-groups.dcs.st-and.ac.uk /~history/Mathematicians/Fresnel.html (2009 words)

	Fresnel Lens Discussion (Site not responding. Last check: 2007-10-22)
		The Fresnel lens was much more efficient at collecting and directing the light rays and produced a beam five times more powerful than the reflector system used previously.
		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)

	Fresnel (Site not responding. Last check: 2007-10-22)
		Fresnel began by undertaking experiments with diffraction and made a breakthrough when he attached a piece of fl paper to one edge of a diffracter and observed that then the bright bands within the shadow vanished.
		One of your commissioners, M Poisson, had deduced from the integrals reported by [Fresnel] the singular result that the centre of the shadow of an opaque circular screen must, when the rays penetrate there at incidences which are only a little more oblique, be just as illuminated as if the screen did not exist.
		Although Fresnel had made many converts to the wave theory of light, even from the most ardent of those previously believing in the corpuscular theory, his assertion that light is a transverse wave was a step too far for most.
	www-groups.dcs.st-andrews.ac.uk /~history/Mathematicians/Fresnel.html (2009 words)

	The Object at Hand - Science Makes a Better Lighthouse Lens (Site not responding. Last check: 2007-10-22)
		Fresnel lenses soon shone along the ragged coastlines of Europe, but surprisingly, America was slower to see the light.
		A Fresnel lens, similar to the one on display at NMAH, was still in use there in September 1900, when waves from the Gulf of Mexico began pounding the coast.
		Today, the principle behind the Fresnel lens is used in the headlights of cars and in the flashing lights on police and emergency vehicles.
	www.smithsonianmag.si.edu /smithsonian/issues99/aug99/object_aug99.html (1302 words)

	Fresnel Effect (Site not responding. Last check: 2007-10-22)
		Fresnel Effect (pronounced "fre-nel," the "s" is silent) - the observation that the amount of reflectance you see on a surface depends on the viewing angle.
		A Fresnel shader will let you specify a specular color for parts of a surface directly facing the camera, and another specular color to be seen on parts of a surface that are perpendicular to the camera.
		In addition to the Fresnel Effect, Augustin-Jean Fresnel is also known as the inventor of the Fresnel Lens, which is still used in lighthouses around the world, and is used in film production on a Fresnel Light.
	www.3drender.com /glossary/fresneleffect.htm (283 words)

	Lighting Instruments: Fresnel Lens Spotlight
		The 6 inch, 750 watt Fresnel is a soft edged, variable beam instrument which is primarily used in the educational and community theatre.
		The Fresnel lens, developed in 1822 (for use in light houses) by Augustin Fresnel (1788-1827), is a less massive form of the more common plano-convex lens.
		Fresnels are generally hung back stage and used as "area lights" on the First Electric or to provide soft edged washes of down and back light.
	www.northern.edu /wild/LiteDes/ld06.htm (528 words)

	The RenderMan Academy - Fresnel Reflectance
		Augustin Jean Fresnel (1788-1827), an early proponent of the wave theory of light propagation, derived the formulas that are still used to predict the reflectance of smooth surfaces, which depends solely on the (complex) refractive index and the angle of incidence.
		The effect of Fresnel reflection is that as the incident angle heads toward grazing the surface, more light is reflected and less is transmitted.
		Fresnel returns the reflection coefficient Kr and refraction (or transmission) coefficient Kt given an incident direction I, the surface normal N, and the relative index of refraction eta.
	www.rendermanacademy.com /docs/Fresnel.htm (631 words)

	Prefect's Pages.. Publications .. IQP .. Fresnel Spotlights
		Fresnel spotlights (pronounced freh-nell) produce a soft-edged beam that is well-suited to washes and specials.
		Fresnels consist of an incandescent lamp, a mirrored parabolic reflector, and a round fresnel lens.
		Fresnel spotlights come in a few sizes, the most common of which are three, six and eight inch.
	www.gweep.net /~prefect/pubs/iqp/node64.html (179 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)

	Fresnel Zone Clearance (Site not responding. Last check: 2007-10-22)
		The Fresnel zone is computed along the path, usually for the distance of each of the terrain points, so the resolution of the computed and plotted Fresnel zone is comparable to the terrain data.
		The Fresnel zone formula shown above is the set of points where the distance from the transmitter to the Fresnel zone, then to the receiver, is longer than the direct path from the transmitter to the receiver.
		For even numbered Fresnel zones (N=2, 4, etc.), the difference between the direct path and the indirect path defined by the Fresnel zone distance, is a multiple of one-half wavelength.
	www.softwright.com /faq/engineering/Fresnel%20Zone%20Clearance.html (505 words)

	Fresnel, Augustin (Site not responding. Last check: 2007-10-22)
		Fresnel realized in 1821 that light waves do not vibrate like sound waves longitudinally, in the direction of their motion, but transversely, at right angles to the direction of the propagated wave.
		Fresnel first had to confirm the wave theory of light.
		Fresnel was born in Broglie, Normandy, and studied in Paris, becoming a civil engineer for the government.
	www.cartage.org.lb /en/themes/Biographies/MainBiographies/F/Fresnel/1.html (206 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 (225 words)

	Inflatable Fresnel Lenses as Concentrators for Solar Power
		The concentric prisms that constitute the Fresnel lens elements could be molded into a sheet that would be bonded to the inner surface of the balloon; typically, this Fresnel-lens sheet would be cast from clear silicone rubber and would be about 250
		At a latitude chosen consistently with the focal length and the radius, the balloon would be anchored on a back plane that would support the solar receiver and would serve as a radiator for dissipating waste heat.
		Fresnel Lenses would be supported on the interior surfaces of spherical and cylindrical balloons.
	www.nasatech.com /Briefs/Mar99/LEW16662.html (500 words)

	Halbo Optics Fresnel Rhombs
		The Fresnel rhomb utilises the different phase changes on internal reflection of the p and s components of an incident plane polarized beam.
		Fresnel rhombs are manufactured in BK7 glass (365nm-900nm), fused silica (230nm-550nm) and calcium fluoride (190nm - 2000nm) to span from the vacuum UV to the far infrared.
		Fresnel rhombs can be supplied unmounted as free components or mounted as shown.
	www.halbo.com /fr_rhmb.htm (472 words)

	Fresnel Selector Language for RDF
		The Fresnel Selector Language (FSL) is a language for modeling traversal paths in RDF graphs.
		It has been designed to address the specific requirements of a path language for the Fresnel RDF display vocabulary and tries to be as simple as possible, reusing as many XPath concepts and syntactic constructs as possible while adapting them to the graph-based RDF data model.
		Such ambiguities are solved in Fresnel by the context of use of the FSL expression, which gives the nature of the primary selection and thus constrains the first (and therefore all) location step(s) (see First Location Step in Fresnel later in this document for details).
	www.w3.org /2005/04/fresnel-info/fsl (5258 words)

	3D Lens.com - Fresnel Lens,Polarizer Fresnel Lens
		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.
		Types of Fresnel lens: positive fresnel lens, negative fresnel lens, fresnel lens array, cylindrical fresnel lens, circular fresnel lens, linear fresnel lens, lenticular fresnel lens, diffraction fresnel, fresnel reflection, fresnel beamsplitter and fresnel prism.
		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 (630 words)

	History of Admiralty Head Lighthouse - The Fresnel Lens
		Augustine Fresnel developed his lens in the early 1800s and it became the standard for most U.S. Lighthouse Service lighthouses across the country.
		Fresnel lenses are comprised of many smaller prisms, individually crafted and suspended in a complex arrangement.
		They concentrate the light into parallel, horizontal beams that may be directed into a narrow, cylindrical beam or a wide, flat beam visible far out to sea.
	www.admiraltyhead.wsu.edu /history/fresnel.html (724 words)

	Fresnell's Equations: Reflection and Transmission
		Fresnel's equations describe the reflection and transmission of electromagnetic waves at an interface.
		For a dielectric medium where Snell's Law can be used to relate the incident and transmitted angles, Fresnel's Equations can be stated in terms of the angles of incidence and transmission.
		Internal reflection implies that the reflection is from an interface to a medium of lesser index of refraction, as from water to air.
	hyperphysics.phy-astr.gsu.edu /hbase/phyopt/freseq.html (424 words)

	[No title] (Site not responding. Last check: 2007-10-22)
		FRESNEL numerical calculations are based on the Fresnel diffraction theory.
		FRESNEL includes such physical phenomena as diffraction, optical imaging, spherical aberration, gain saturation effects in amplifiers, pulse shape distortion and nonlinear effects in media.
		FRESNEL is addressed to: scientists and engineers, lecturers in laser optics, students.
	www.wavesimsoft.com (128 words)

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