Fresnel Lens displayed in the Musée national de la marine in Paris, France

A Fresnel lens (pronounced ['frɛz. nəl] or [freɪ'nɛl]) is a type of lens invented by French physicist Augustin-Jean Fresnel. A lens is an optical device with perfect or approximate Axial symmetry which transmits and refracts Light, converging or diverging This article is about the country For a topic outline on this subject see List of basic France topics. Physics (Greek Physis - φύσις in everyday terms is the Science of Matter and its motion. Originally developed for lighthouses, the design enables the construction of lenses of large aperture and short focal length without the weight and volume of material which would be required in conventional lens design. A lighthouse is a Tower, building or framework designed to emit light from a system of lamps and lenses or in older times from a fire and used as an The focal length of an optical system is a measure of how strongly it converges (focuses or diverges (diffuses Light. A lens is an optical device with perfect or approximate Axial symmetry which transmits and refracts Light, converging or diverging Compared to earlier lenses, the Fresnel lens is much thinner, thus passing more light and allowing lighthouses to be visible over much longer distances. A lighthouse is a Tower, building or framework designed to emit light from a system of lamps and lenses or in older times from a fire and used as an

Development

The idea of creating a thinner, lighter lens by making it with separate sections mounted in a frame is often attributed to Georges-Louis Leclerc, Comte de Buffon. Georges-Louis Leclerc fr Comte de Buffon ( September 7, 1707 April 16, 1788) was a French naturalist, mathematician biologist ^[1] However, it is difficult to find any other sources that link Buffon to work with optics. French physicist and engineer Augustin-Jean Fresnel is most often given credit for the development of this lens for use in lighthouses. According to Smithsonian, the first Fresnel lens was used in 1823 in the Cordouan lighthouse at the mouth of the Gironde estuary; its light could be seen from more than 20 miles out. Smithsonian is a monthly Magazine published by the Smithsonian Institution in Washington D Year 1823 ( MDCCCXXIII) was a Common year starting on Wednesday (link will display the full calendar of the Gregorian Calendar (or a Common Cordouan is a Lighthouse located 7 km at sea geographically The Gironde is a navigable Estuary (often falsely referred to as a River) in southwest France and is formed from the meeting of the rivers Dordogne ^[2] Scottish physicist Sir David Brewster is credited with convincing The United Kingdom to use these lenses in their lighthouses. Sir David Brewster, FRS ( 11 December 1781 &ndash 10 February 1868) was a Scottish scientist inventor and writer ^[3][4]

Detailed information

The Fresnel lens 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.

In the first (and largest) variations of the lens, each of these zones was a different prism. Though a lens might look like a single piece of glass, closer examination reveals that it is many small pieces. It was not until modern computer-controlled milling equipment (CNC) could turn out large complex pieces that these lenses were single pieces of glass. The abbreviation CNC stands for computer numerical control, and refers specifically to a computer "controller" that reads G-code

For each of these zones, the overall thickness of the lens is decreased, effectively chopping the continuous surface of a standard lens into a set of surfaces of the same curvature, with discontinuities between them. This allows a substantial reduction in thickness (and thus weight and volume of material) of the lens, at the expense of reducing the imaging quality of the lens.

Graphic examples

1: Cross section of a Fresnel lens 2: Cross section of a conventional plano-convex lens of equivalent power

Close-up of a lighthouse lens

Uses

Cape Meares Lighthouse (Oregon, USA) first-order Fresnel lens

For the reasons given above, Fresnel lenses tend to be used in applications where imaging quality is not critical, or where the bulk of a solid lens would be prohibitive. A lens is an optical device with perfect or approximate Axial symmetry which transmits and refracts Light, converging or diverging The Cape Meares Light is an inactive Lighthouse on the coast of Oregon. 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. An overhead projector (OHP is a variant of Slide projector that is used to display images to an audience Television ( TV) is a widely used Telecommunication medium for sending ( Broadcasting) and receiving moving Images, either monochromatic magnifying glass (called a hand lens in laboratory contexts is a convex lens which is used to produce a magnified Image of an object Fresnel lenses have been used to increase the visual size of CRT displays in pocket televisions, notably the Sinclair TV80. Television ( TV) is a widely used Telecommunication medium for sending ( Broadcasting) and receiving moving Images, either monochromatic Sinclair Research Ltd is a consumer electronics company founded by Sir Clive Sinclair in Cambridge, England (originally as Sinclair Radionics in 1961 to The Sinclair TV80, also known as the Flat Screen Pocket TV or FTV1, was a pocket television launched by Sinclair Research in 1984. Fresnel lenses are also used in traffic lights and solar forges. The traffic light, also known as traffic signal, stop light, traffic lamp, stop-and-go lights, robot or semaphore, A solar forge is a device that uses the power of the Sun to melt materials such as Asphalt.

Fresnel lenses are also used to correct several visual disorders. These disorders include several ocular motility disorders including strabismus.

Fresnel lenses can concentrate much more sunlight than normal convex lenses, and melt certain materials and instantly ignite others. Commercial Fresnel lenses are often available from scientific supply stores and are made of bendable plastic. They can be employed in homemade solar cookers and solar collectors to heat water for domestic use. A solar oven or solar cooker is a device which uses Sunlight as its energy source

Perhaps the most widespread use of Fresnel lenses was in automobile headlamps, where they allow the roughly-parallel beam from the parabolic reflector to be shaped to meet requirements for dipped and main beam patterns, often both in the same headlamp unit (such as the European H4 design). For reasons of cost, weight and impact resistance, newer cars have dispensed with glass Fresnel lenses, using multi-faceted reflectors with plain polycarbonate lenses. However, Fresnel lenses continue to be widely used in automobile tail, marker and backup lights.

High-quality glass Fresnel lenses were used in lighthouses; most are now retired from service. Lighthouse Fresnel lens systems typically include extra annular prismatic elements, arrayed in faceted domes above and below the central planar Fresnel, in order to catch all light emitted from the light source. In Optics, a prism is a transparent optical element with flat polished surfaces that refract Light. The light path through these elements can include an internal reflection, rather than the simple refraction in the planar Fresnel element. Refraction is the change in direction of a Wave due to a change in its Speed.

Glass Fresnel lenses also are used in lighting instruments for theater and motion pictures (see Fresnel lantern); such instruments are often called simply Fresnels. Theatre (or theater, see spelling differences) is the branch of the Performing arts defined by Bernard Beckerman as what "occurs when one 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 The entire instrument consists of a metal housing, reflector, lamp assembly, and Fresnel lens. A holder in front of the lens can hold a colored plastic film (gel) to tint the light or wire screens or frosted plastic to diffuse it. Many Fresnel instruments allow the lamp to be moved relative to the lens focal point, to increase or decrease the size of the light beam. Track listing Child – 516 All I Need – 355 The Fresnel lens is useful in the making of motion pictures not only because of its ability to focus the beam brighter than a typical lens, but also because the light is a relatively consistent intensity across the entire width of the beam of light.

Optical Landing System on US Navy aircraft carrier USS Dwight D. Eisenhower

Aircraft carriers typically use Fresnel lenses in their optical landing system. Construction On 29 June 1970 Newport News Shipbuilding of Newport News, Virginia was awarded the contract for construction An aircraft carrier is a Warship designed with The "meatball" light aids the pilot in maintaining proper glideslope for the landing. In the center are amber and red lights composed of Fresnel lenses. Although the lights are always on, the angle of the lens from the pilot's point of view determines the color and position of the visible light. If the lights appear above the green horizontal bar, the pilot is too high. If it is below, the pilot is too low, and if the lights are red, the pilot is very low.

New applications have appeared in solar energy, where Fresnel lenses are used to concentrate sunlight (with a ratio of almost 500) onto solar cells. Thus the active solar cell surface can be reduced to a fraction compared to conventional solar modules. A solar cell or photovoltaic cell is a device that converts Solar energy into Electricity by the photovoltaic effect. This offers a considerable cost-saving potential by low material consumption, and it is possible to use high-quality and expensive solar cells, which achieve a very high efficiency under concentration due to thermodynamic effects. ^[5]

Fresnel reflectors are also currently being incorporated into next-generation solar thermal energy systems. See solar power for more information. Solar energy is the Light and radiant heat from the Sun that powers Earth 's Climate and Weather and sustains Life The Polaroid SX-70 camera used a Fresnel reflector as part of its viewing system. The SX-70 is a folding Single lens reflex Land Camera which was produced by the Polaroid Corporation from 1972-1977

Multi-focal Fresnel lens are also used as a part of retina identification camera, where they provide multiple in- and out-of-focus images of a fixation target inside the camera. A retinal scan is a Biometric technique that uses the unique patterns on a person's Retina to identify them For virtually all users, at least one of the images will be in focus, thus allowing correct eye alignment.

Fresnel lens has seen applications in to enhancing passenger reading lights on Airbus aircraft. In a dark cabin, the focused beam of light does not dazzle neighboring passengers.

Fresnel lenses have also been used in the field of popular entertainment. The British rock artist Peter Gabriel made use of them in his early solo live performances to magnify the size of his head, in contrast to the rest of his body, for dramatic and comic effect. Peter Brian Gabriel (born 13 February 1950 in Chobham, Surrey, England) is an English Musician and Songwriter. In the Terry Gilliam film Brazil, plastic Fresnel screens appear ostensibly as magnifiers for the small CRT monitors used throughout the offices of the Ministry of Information. Terrence Vance Gilliam (born 22 November 1940) is an American -born British Writer, Filmmaker, Animator and member Brazil is a 1985 Dystopian Black comedy film directed by Terry Gilliam. However, they occasionally appear between the actors and the camera, distorting the scale and composition of the scene to humorous effect.

Lens of Loschen-lighthouse, Bremerhaven

Lens of a lighthouse in Rozewie, Poland

Sizes of lighthouse lenses

Fresnel's lighthouse lenses fell into six orders based on their focal length. Bremerhaven (bʁeːmɐˈhaːfən is the seaport of the free city and federal state of Bremen, Germany. A lighthouse is a Tower, building or framework designed to emit light from a system of lamps and lenses or in older times from a fire and used as an Rozewie is a Headland (cape in Poland It's one of Extreme points of Poland - the most northern part of Poland - although that claim can vary depending on a Poland (Polska officially the Republic of Poland The largest (first order) lens has a focal length of 920 mm (36 in), and an optical area 2590 mm (8. 5 ft) high. The complete assembly is about 3. 7 m (12 ft) tall and 1. 8 m (6 ft) wide. The smallest (sixth order) has a focal length of 150 mm (5. 9 in) and an optical area 433 mm (17 in) high. ^[6][7]

Subsequent development extended this to seventh and eighth orders, an intermediate three-and-one-half order, and two orders even larger than first: mesoradial and hyperradial. Hyperradiant fresnel lenses are Fresnel lenses larger than "first order" lenses so they are larger than 12 feet (3

Projection uses

Fresnel lenses of different focal lengths (one collimator, and one collector) are used in commercial and DIY projection. A collimator is a device that narrows a beam of particles or waves The collimator lens has the lower focal length, and is placed closer to the light source, and the collector lens, which focuses the light into the triplet lens, is placed after the projection image (an active matrix LCD panel in LCD projectors). An active matrix Liquid crystal display ( AMLCD) is a type of Flat panel display, currently the overwhelming choice of Notebook computer An LCD projector is a type of Video projector for displaying video images or computer data on a screen or other flat surface

Generating solar power

Fresnel reflectors are used in Concentrated Solar Power (CSP) plants to concentrate solar energy from the sun. Solar thermal energy ( STE) is a technology for harnessing Solar energy for Thermal energy ( Heat)

References

Additional reading

• "The Fresnel Lens. " The Keeper's Log (Winter 1985), pp. 12-14.
• Lighthouses, Illuminants, Lenses Engineering and Augustin Fresnel, An Historical Bibliography, United States Coast Guard.
• United States Coast Guard, Aids to Navigation, (Washington, DC: U. S. Government Printing Office, 1945).
• United States Coast Guard, Aids to Navigation Historical Bibliography.

External links

• Lighthouse Getaway: Fresnel lens (contains photographs. )
• Pepper, Terry. Seeing the Light: Lighthouses on the western Great Lakes.
• Random Destructive Acts via Focused Solar Radiation.