title: "Little penguin" content: Little penguin The little penguin ("Eudyptula minor") is the smallest species of penguin. It grows to an average of in height and in length, though specific measurements vary by subspecies. It is found on the coastlines of southern Australia and New Zealand, with possible records from Chile. In Australia, they are often called fairy penguins because of their small size. In New Zealand, they are more commonly known as little blue penguins or blue penguins owing to their slate-blue plumage. They are also known by their Māori name: kororā. The little penguin was first described by German naturalist Johann Reinhold


title: "Little penguin" content: Forster in 1781. Several subspecies are known, but a precise classification of these is still a matter of dispute. The holotypes of the subspecies "E. m. variabilis" and "Eudyptula minor chathamensis" are in the collection of the Museum of New Zealand Te Papa Tongarewa. The white-flippered penguin is sometimes considered a subspecies, sometimes a distinct species, and sometimes a morph. Genetic analyses indicate that the Australian and Otago (southeastern coast of South Island) little penguins may constitute a distinct species. In this case it the specific name "minor" would devolve on it, with the specific name "novaehollandiae" suggested for the


title: "Little penguin" content: other populations; This interpretation suggests that "E. novaehollandiae" individuals arrived in New Zealand between AD 1500 and 1900 while the local "E. minor" population had declined, leaving a genetic opening for a new species. Mitochondrial and nuclear DNA evidence suggests the split between "Eudyptula" and "Spheniscus" occurred around 25 million years ago, with the ancestors of the white-flippered and little penguins diverging about 2.7 million years ago. Like those of all penguins, the little penguin's wings have developed into flippers used for swimming. The little penguin typically grows to between tall and usually weighs about 1.5 kg on average (3.3


title: "Little penguin" content: lb). The head and upper parts are blue in colour, with slate-grey ear coverts fading to white underneath, from the chin to the belly. Their flippers are blue in colour. The dark grey-black beak is 3–4 cm long, the irises pale silvery- or bluish-grey or hazel, and the feet pink above with black soles and webbing. An immature individual will have a shorter bill and lighter upperparts. Like most seabirds, they have a long lifespan. The average for the species is 6.5 years, but flipper ringing experiments show in very exceptional cases up to 25 years in captivity. The little


title: "Little penguin" content: penguin breeds along the entire coastline of New Zealand, the Chatham Islands, and southern Australia (including roughly 20,000 pairs on Babel Island). Australian colonies exist in New South Wales, Victoria, Tasmania, South Australia, and Western Australia. Little penguins have also been reported from Chile (where they are known as "pingüino pequeño" or "pingüino azul") (Isla Chañaral 1996, Playa de Santo Domingo, San Antonio, 16 March 1997) and South Africa, but it is unclear whether these birds were vagrants. As new colonies continue to be discovered, rough estimates of the world population are around 350,000-600,000 animals. Overall, little penguin populations in


title: "Little penguin" content: New Zealand have been decreasing. Some colonies have gone extinct and others continue to be at risk. Some new colonies have been established in urban areas. The species is not considered endangered in New Zealand, with the exception of the white-flippered subspecies found only on Banks Peninsula and nearby Motunau Island. Since the 1960s, the mainland population has declined by 60-70%; though a small increase has occurred on Motunau Island. Australian little penguin colonies primarily exist on offshore islands, where they are protected from feral terrestrial predators and human disturbance. Colonies are found from Port Stephens in northern New South


title: "Little penguin" content: Wales around the southern coast to Fremantle, Western Australia. An endangered population of little penguins exists at Manly, in Sydney's North Harbour. The population is protected under the NSW Threatened Species Conservation Act 1995 and has been managed in accordance with a Recovery Plan since the year 2000. The population once numbered in the hundreds, but has decreased to around 60 pairs of birds. The decline is believed to be mainly due to loss of suitable habitat, attacks by foxes and dogs and disturbance at nesting sites. The largest colony in New South Wales is on Montague Island. Up to


title: "Little penguin" content: 8000 breeding pairs are known to nest there each year. A population of about 5,000 breeding pairs exists on Bowen Island. The colony has increased from 500 pairs in 1979 and 1500 pairs in 1985. During this time, the island was privately leased. The island was vacated in 1986 and is currently controlled by the federal government. In South Australia, many little penguin colony declines have been identified across the state. In some cases, colonies have declined to extinction (including the Neptune Islands, West Island, Wright Island, Pullen Island and several colonies on western Kangaroo Island), while others have declined


title: "Little penguin" content: from thousands of animals to few (Granite Island and Kingscote). A report released in 2011 presented evidence supporting the listing of the statewide population or the more closely monitored sub-population from St. Vincent's Gulf as Vulnerable under South Australia's "National Parks & Wildlife Act 1972". As of 2014, the little penguin is not listed as a species of conservation concern, despite ongoing declines at many colonies. Tasmanian little penguin population estimates range from 110,000–190,000 breeding pairs of which less than 5% are found on mainland Tasmania. Ever-increasing human pressure is predicted to result in the extinction of colonies on mainland


title: "Little penguin" content: Tasmania. The largest colony of little penguins in Victoria is located at Phillip Island, where the nightly 'parade' of penguins across Summerland Beach has been a major tourist destination, and more recently a major conservation effort, since the 1920s. Phillip Island is home to an estimated 32,000 breeding pairs (70,000 birds). Little penguins can also be seen in the vicinity of the St Kilda, Victoria pier and breakwater. The breakwater is home to a colony of little penguins which have been the subject of a conservation study since 1986. Little penguin habitats also exist at a number of other locations,


title: "Little penguin" content: including London Arch and The Twelve Apostles along the Great Ocean Road, Wilson's Promontory and Gabo Island. The largest colony of little penguins in Western Australia is believed to be located on Penguin Island, where an estimated 1,000 pairs nest during winter. Penguins are also known to nest on Garden Island and Carnac Island which lie north of Penguin Island. Many islands along Western Australia's southern coast are likely to support little penguin colonies, though the status of these populations are largely unknown. An account of little penguins on Bellinger Island published in 1928 numbered them in their thousands. Visiting


title: "Little penguin" content: naturalists in November 1986 estimated the colony at 20 breeding pairs. The account named another substantial colony 12 miles from Bellinger Island and the same distance from Cape Pasley. Little penguins are known to breed on some islands of the Recherche Archipelago, including Woody Island where day-tripping tourists can view the animals. A penguin colony exists on Mistaken Island in King George Sound near Albany. Historical accounts of little penguins on Newdegate Island at the mouth of Deep River and on Breaksea Island near Torbay also exist. In 1930 in Tasmania, it was believed that little penguins were competing with


title: "Little penguin" content: mutton-birds, which were being commercially exploited. An "open season" in which penguins would be permitted to be killed was planned in response to requests from members of the mutton-birding industry. The impacts of human habitation in proximity to little penguin colonies include collisions with vehicles, direct harassment, burning and clearing of vegetation and housing development. Penguins are vulnerable to interference by humans, especially while they are ashore during molt or nesting periods. In 1949, penguins on Phillip Island in Victoria became victims of human cruelty, with some kicked and others thrown off a cliff and shot at. These acts of


title: "Little penguin" content: cruelty prompted the state government to fence off the rookeries. More recent examples of destructive interference can be found at Granite island, where in 1994 a penguin chick was taken from a burrow and abandoned on the mainland, a burrow containing penguin chicks was trampled and litter was discarded down active burrows. In 1998, two incidents in six months resulted in penguin deaths. The latter, which occurred in May, saw 13 penguins apparently kicked to death. In March 2016, two little penguins were kicked and attacked by humans during separate incidents at the St Kilda colony, Victoria. In 2018, 20-year-old


title: "Little penguin" content: Tasmanian man Joshua Leigh Jeffrey was fined $82.50 in court costs and sentenced to 49 hours of community service at Burnie Magistrates Court on 25 June 2018 after killing nine little penguins at Sulfur Creek in North West Tasmania on 1 January 2016 by beating them with a stick. Dr Eric Woehler from conservation group Birds Tasmania denounced the perceived leniency of the sentence which he said placed minimal value on Tasmania's wildlife and set an "unwelcome precedent". Following an appeal by prosecutors, Jeffrey had his sentence doubled on 15 October 2018. The office of the Director of Public Prosecutions


title: "Little penguin" content: said it considered the original sentence to be manifestly inadequate. The original sentence was set aside, and Jeffrey was sentenced to two months in prison, suspended on the condition of him committing no offences for a year that are punishable by imprisonment. His community order was also doubled to 98 hours. Also in 2018, a dozen little penguin carcasses were found in a garbage bin at Low Head, Tasmania prompting an investigation into the causes of death. Some little penguins are drowned when amateur fishermen set gill nets near penguin colonies. Discarded fishing line can also present an entanglement risk


title: "Little penguin" content: and contact can result in physical injury, reduced mobility or drowning. In 2014, a group of 25 dead little penguins were found on Altona Beach in Victoria. Necropsies concluded that the animals had died after becoming entangled in net fishing equipment, prompting community calls for a ban on net fishing in Port Phillip Bay. In the 20th century, little penguins were intentionally shot or caught by fishermen to use as bait in pots for catching crayfish (Southern rock lobster) or by line fishermen. Colonies were targeted for this purpose in various parts of Tasmania including Bruny Island and West Island,


title: "Little penguin" content: South Australia. A study in Perth from 2003 to 2012 found that the main cause of mortality was trauma, most likely from watercraft, leading to a recommendation for management strategies to avoid watercraft strikes. Oil spills can be lethal for penguins and other sea birds. Oil is toxic when ingested and penguins' buoyancy and the insulative quality of their plumage is damaged by contact with oil. Little penguin populations have been significantly affected during two major oil spills at sea: the Iron Baron oil spill off Tasmania's north coast in 1995 and the grounding of the Rena off New Zealand


title: "Little penguin" content: in 2011. Plastics are swallowed by little penguins, who mistake them for prey items. They present a choking hazard and also occupy space in the animal's stomach. Indigestible material in a penguin's stomach can contribute to malnutrition or starvation. Other larger plastic items, such as bottle packaging rings, can become entangled around penguins' necks, affecting their mobility. Threats to little penguin populations include predation (both adult and nest predation) by a variety of terrestrial animals including cats, dogs, rats, foxes, large reptiles, ferrets and stoats. Due to their diminutive size and the introduction of new predators, some colonies have been


title: "Little penguin" content: reduced in size by as much as 98% in just a few years, such as the small colony on Middle Island, near Warrnambool, Victoria, which was reduced from approximately 600 penguins in 2001 to less than 10 in 2005. Because of this threat of colony collapse, conservationists successfully pioneered an experimental technique using Maremma Sheepdogs to protect the colony and fend off would-be predators, with numbers reaching 100 by 2017. Uncontrolled dogs or feral cats can have sudden and severe impacts on penguin colonies (more than the penguin's natural predators) and may kill many individuals. Examples of colonies affected by


title: "Little penguin" content: dog attacks include Manly, New South Wales, Penneshaw, South Australia, Red Chapel Beach, Tasmania, Low Head, Tasmania, Penguin Island, Western Australia and Little Kaiteriteri Beach, New Zealand. A suspected stoat or ferret attack at Doctor's Point near Dunedin, New Zealand claimed the lives of 29 little blue penguins in November 2014. A fox was believed responsible for the deaths of 53 little penguins over several nights on Granite Island in 1994. In June 2015, 26 penguins from the Manly colony were killed in 11 days. A fox believed responsible was eventually shot in the area and an autopsy is expected


title: "Little penguin" content: to prove or disprove its involvement. In November 2015 a fox entered the little penguin enclosure at the Melbourne Zoo and killed 14 penguins, prompting measures to further "fox proof" the enclosure. Variation in prey abundance and distribution from year to year causes young birds to be washed up dead from starvation or in weak condition. Little penguins in the wild are sometimes preyed upon by long-nosed fur seals. A study conducted by researchers from the South Australian Research and Development Institute found that roughly 40 percent of seal droppings in South Australia's Granite Island area contained little penguin remains.


title: "Little penguin" content: They are also preyed upon by white-bellied sea eagles. These large birds-of-prey are endangered in South Australia and not considered a threat to colony viability. On land, little penguins are vulnerable to attack from domestic and feral dogs and cats. Attacks on Kangaroo Island, at Manly in Tasmania and in New Zealand have resulted in significant impacts to several populations. Management strategies to mitigate the risk of attack include establishing dog-free zones near penguin colonies and introducing regulations to ensure dogs to remain on leashes at all times in adjacent areas. Little penguins on Middle Island off Warrnambool, Victoria were


title: "Little penguin" content: subject to heavy predation by foxes, which were able to reach the island at low tide by a tidal sand bridge. The deployment of Maremma sheepdogs to protect the penguin colony has deterred the foxes and enabled the penguin population to rebound. This is in addition to the support from groups of volunteers who work to protect the penguins from attack at night. The first Maremma sheepdog to prove the concept was Oddball, whose story inspired a feature film of the same name, released in 2015. In December 2015, the BBC reported, "The current dogs patrolling Middle Island are Eudy


title: "Little penguin" content: and Tula, named after the scientific term for the fairy penguin: Eudyptula. They are the sixth and seventh dogs to be used and a new puppy is being trained up [...] to start work in 2016. In Sydney, snipers have been deployed to protect a colony of little penguins. This effort is in addition to support from local volunteers who work to protect the penguins from attack at night. Little penguins are diurnal and like many penguin species, spend the largest part of their day swimming and foraging at sea. During the breeding and chick-rearing seasons, little penguins leave their


title: "Little penguin" content: nest at sunrise, forage for food throughout the day and return to their nests just after dusk. Thus, sunlight, moonlight and artificial lights can affect the behaviour of attendance to the colony. Also, increased wind speeds negatively affect the little penguins' efficiency in foraging for chicks, but for reasons not yet understood. Little penguins preen their feathers to keep them waterproof. They do this by rubbing a tiny drop of oil onto every feather from a special gland above the tail. These birds feed by hunting small clupeoid fish, cephalopods and crustaceans, for which they travel and dive quite extensively.


title: "Little penguin" content: In New Zealand, important prey items include arrow squid, slender sprat, Graham's gudgeon, red cod and ahuru. Since the year 2000, the little penguins of Port Phillip Bay's diet has consisted mainly of barracouta, anchovy, and arrow squid. Sardines previously featured more prominently in southern Australian little penguin diets prior to mass sardine mortality events of the 1990s. These mass mortality events affected sardine stocks over 5,000 kilometres of coastline. Jellyfish including species in the genera "Chrysaora" and "Cyanea" were found to be actively sought-out food items, while they previously had been thought to be only accidentally ingested. Similar preferences


title: "Little penguin" content: were found in the Adélie penguin, yellow-eyed penguin and Magellanic penguin. They are generally inshore feeders. The use of data loggers has provided information of the diving behaviour of little penguins. 50% of their dives go no deeper than 2 m and the mean diving time is 21 seconds. Yet, they are able to dive as deep as 20 m and remained submerged as long as 60 seconds. Little penguins play an important role in the ecosystem as not only a predator to parasites but also a host. Recent studies have shown a new species of feather mite that feeds


title: "Little penguin" content: on the preening oil on the feathers of the penguin. Little penguins mature at different ages. The female matures at 2 years old. The male, however, matures at 3 years old. Little penguins only remain faithful to their partner in breeding seasons and whilst hatching eggs. At other times of the year they do tend to swap burrows. They exhibit site fidelity to their nesting colonies and nesting sites over successive years. Little penguins can breed as isolated pairs, in colonies, or semi-colonially. Nests are situated close to the sea in burrows excavated by the birds or other species, or


title: "Little penguin" content: in caves, rock crevices, under logs or in or under a variety of man-made structures including nest boxes, pipes, stacks of wood or timber, and buildings. They are monogamous within a breeding season, and share incubating and chick-rearing duties. They are the only species of penguin capable of producing more than one clutch of eggs per breeding season, but few populations do so. The timing of breeding seasons varies across the species' range. Eastern Australian populations (including at Phillip Island, Victoria) lay their eggs from July through December. In South Australia's Gulf St. Vincent, eggs are laid between April and


title: "Little penguin" content: October. The one or two white or lightly mottled brown eggs are laid with rarer second (or even third) clutches following. Incubation takes up to 36 days. Chicks are brooded for 18–38 days and fledge after 7–8 weeks. On Australia's east coast, chicks are raised from August through March. In Gulf St. Vincent, chicks are raised from June through November. Little penguins typically return to their colonies to feed their chicks at dusk. The birds tend to come ashore in small groups to provide some defence against predators, which might pick off individuals one by one. In Australia, the strongest


title: "Little penguin" content: colonies are usually on cat-free and fox-free islands. However, the population on Granite Island (which is a fox, cat and dog-free island) has been severely depleted, from around 2000 penguins in 2001 down to 146 in 2009. Little penguins have long been a curiosity to humans, and to children in particular. Captive animals are often exhibited in zoos. Historically, the animals have also been used as bait to catch Southern rock lobster, captured for amusement and eaten by ship-wrecked sailors and castaways to avoid starvation. They have also been the victims of malicious attacks by humans and incidental bycatch by


title: "Little penguin" content: fishermen using nets. The sites of many breeding colonies have developed into tourist destinations which provide an economic boost for coastal and island communities in Australia and New Zealand. These locations also often provide facilities and volunteer staff to support population surveys, habitat improvement works and little penguin research programs. At Phillip Island, Victoria, a viewing area has been established at the Phillip Island Nature Park to allow visitors to view the nightly "penguin parade". Lights and concrete stands have been erected to allow visitors to see but not photograph or film the birds (this is because it can blind


title: "Little penguin" content: or scare them) interacting in their colony. In Bicheno, Tasmania, evening penguin viewing tours are offered by a local tour operator at a rookery on private land. A similar sunset tour is offered at Low Head, near the mouth of the River Derwent on Tasmania's north coast. Observation platforms exist near some of Tasmania's other little penguin colonies, including Bruny Island and Lillico Beach near Devonport. South of Perth, Western Australia, visitors to Penguin Island are able to view penguin feeding within a penguin rehabilitation centre and may also encounter wild penguins ashore in their natural habitat. The island is


title: "Little penguin" content: accessible via a short passenger ferry ride, and visitors depart the island before dusk to protect the colony from disturbance. Visitors to Kangaroo Island, South Australia, have nightly opportunities to observe penguins at the Kangaroo Island Marine Centre in Kingscote and at the Penneshaw Penguin Centre. Granite Island at Victor Harbor, South Australia continues to offer guided tours at dusk, despite its colony dropping from thousands in the 1990s to dozens in 2014. There is also a Penguin Centre located on the island where the penguins can be viewed in captivity. In the Otago, New Zealand town of Oamaru, visitors


title: "Little penguin" content: may view the birds returning to their colony at dusk. In Oamaru it is not uncommon for penguins to nest within the cellars and foundations of local shorefront properties, especially in the old historic precinct of the town. More recently, little penguin viewing facilities have been established at Pilots Beach on the Otago Peninsula in Dunedin, New Zealand. Here visitors are guided by volunteer wardens to watch penguins returning to their burrows at dusk. Several efforts have been made to improve breeding sites on Kangaroo Island, including augmenting habitat with artificial burrows and revegetation work. The Knox School's habitat restoration


title: "Little penguin" content: efforts were filmed and broadcast in 2008 by "Totally Wild". Exhibits currently exist at the Adelaide Zoo, Melbourne Zoo, the National Zoo & Aquarium in Canberra, Perth Zoo, Caversham Wildlife Park (Perth), Sea Life Sydney Aquarium and the Taronga Zoo in Sydney. A colony of little penguins is also exhibited at Sea World, on the Gold Coast, Queensland, Australia. In early March, 2007, 25 of the 37 penguins died from an unknown toxin following a change of gravel in their enclosure. It is still not known what caused the deaths of the little penguins, and it was decided not to


title: "Little penguin" content: return the 12 surviving penguins to the same enclosure in which the penguins became ill. A new enclosure for the little penguin colony was opened at Sea World in 2008. Exhibits currently exist at the Auckland Zoo, the Wellington Zoo and the National Aquarium of New Zealand. A colony of little blue penguins exists at the New England Aquarium in Boston, Massachusetts. The penguins are one of three species on exhibit and are part of the Association of Zoos and Aquariums' Species Survival Plan for little blue penguins. Linus Torvalds, the original creator of Linux (a popular operating system kernel),


title: "Little penguin" content: was once pecked by a little penguin while on holiday in Australia. Reportedly, this encounter encouraged Torvalds to select Tux as the official Linux mascot. A Linux kernel programming challenge called the Eudyptula Challenge has attracted thousands of persons; its creator(s) use the name "Little Penguin". Penny the Little Penguin was the mascot for the 2007 FINA World Swimming Championships held in Melbourne, Victoria. Little penguin The little penguin ("Eudyptula minor") is the smallest species of penguin. It grows to an average of in height and in length, though specific measurements vary by subspecies. It is found on the coastlines


title: "Light-emitting diode" content: Light-emitting diode A light-emitting diode (LED) is a two-lead semiconductor light source. It is a p–n junction diode that emits light when activated. When a suitable current is applied to the leads, electrons are able to recombine with electron holes within the device, releasing energy in the form of photons. This effect is called electroluminescence, and the color of the light (corresponding to the energy of the photon) is determined by the energy band gap of the semiconductor. LEDs are typically small (less than 1 mm) and integrated optical components may be used to shape the radiation pattern. Appearing as


title: "Light-emitting diode" content: practical electronic components in 1962, the earliest LEDs emitted low-intensity infrared light. Infrared LEDs are still frequently used as transmitting elements in remote-control circuits, such as those in remote controls for a wide variety of consumer electronics. The first visible-light LEDs were of low intensity and limited to red. Modern LEDs are available across the visible, ultraviolet, and infrared wavelengths, with very high brightness. Early LEDs were often used as indicator lamps for electronic devices, replacing small incandescent bulbs. They were soon packaged into numeric readouts in the form of seven-segment displays and were commonly seen in digital clocks. Recent


title: "Light-emitting diode" content: developments have produced LEDs suitable for environmental and task lighting. LEDs have led to new displays and sensors, while their high switching rates are useful in advanced communications technology. LEDs have many advantages over incandescent light sources, including lower energy consumption, longer lifetime, improved physical robustness, smaller size, and faster switching. Light-emitting diodes are used in applications as diverse as aviation lighting, automotive headlamps, advertising, general lighting, traffic signals, camera flashes, lighted wallpaper and medical devices. They are also significantly more energy efficient and, arguably, have fewer environmental concerns linked to their disposal. Unlike a laser, the color of light


title: "Light-emitting diode" content: emitted from an LED is neither coherent nor monochromatic, but the spectrum is narrow with respect to human vision, and for most purposes the light from a simple diode element can be regarded as functionally monochromatic. Electroluminescence as a phenomenon was discovered in 1907 by the British experimenter H. J. Round of Marconi Labs, using a crystal of silicon carbide and a cat's-whisker detector. Russian inventor Oleg Losev reported creation of the first LED in 1927. His research was distributed in Soviet, German and British scientific journals, but no practical use was made of the discovery for several decades. In


title: "Light-emitting diode" content: 1936, Georges Destriau observed that electroluminescence could be produced when zinc sulphide (ZnS) powder is suspended in an insulator and an alternating electrical field is applied to it. In his publications, Destriau often referred to luminescence as Losev-Light. Destriau worked in the laboratories of Madame Marie Curie, also an early pioneer in the field of luminescence with research on radium. Kurt Lehovec, Carl Accardo, and Edward Jamgochian explained these first light-emitting diodes in 1951 using an apparatus employing SiC crystals with a current source of battery or pulse generator and with a comparison to a variant, pure, crystal in 1953.


title: "Light-emitting diode" content: Rubin Braunstein of the Radio Corporation of America reported on infrared emission from gallium arsenide (GaAs) and other semiconductor alloys in 1955. Braunstein observed infrared emission generated by simple diode structures using gallium antimonide (GaSb), GaAs, indium phosphide (InP), and silicon-germanium (SiGe) alloys at room temperature and at 77 kelvins. In 1957, Braunstein further demonstrated that the rudimentary devices could be used for non-radio communication across a short distance. As noted by Kroemer Braunstein "…had set up a simple optical communications link: Music emerging from a record player was used via suitable electronics to modulate the forward current of a


title: "Light-emitting diode" content: GaAs diode. The emitted light was detected by a PbS diode some distance away. This signal was fed into an audio amplifier and played back by a loudspeaker. Intercepting the beam stopped the music. We had a great deal of fun playing with this setup." This setup presaged the use of LEDs for optical communication applications. In September 1961, while working at Texas Instruments in Dallas, Texas, James R. Biard and Gary Pittman discovered near-infrared (900 nm) light emission from a tunnel diode they had constructed on a GaAs substrate. By October 1961, they had demonstrated efficient light emission and


title: "Light-emitting diode" content: signal coupling between a GaAs p-n junction light emitter and an electrically isolated semiconductor photodetector. On August 8, 1962, Biard and Pittman filed a patent titled "Semiconductor Radiant Diode" based on their findings, which described a zinc-diffused p–n junction LED with a spaced cathode contact to allow for efficient emission of infrared light under forward bias. After establishing the priority of their work based on engineering notebooks predating submissions from G.E. Labs, RCA Research Labs, IBM Research Labs, Bell Labs, and Lincoln Lab at MIT, the U.S. patent office issued the two inventors the patent for the GaAs infrared (IR)


title: "Light-emitting diode" content: light-emitting diode (U.S. Patent US3293513), the first practical LED. Immediately after filing the patent, Texas Instruments (TI) began a project to manufacture infrared diodes. In October 1962, TI announced the first commercial LED product (the SNX-100), which employed a pure GaAs crystal to emit a 890 nm light output. In October 1963, TI announced the first commercial hemispherical LED, the SNX-110. The first visible-spectrum (red) LED was developed in 1962 by Nick Holonyak, Jr. while working at General Electric. Holonyak first reported his LED in the journal "Applied Physics Letters" on December 1, 1962. M. George Craford, a former graduate


title: "Light-emitting diode" content: student of Holonyak, invented the first yellow LED and improved the brightness of red and red-orange LEDs by a factor of ten in 1972. In 1976, T. P. Pearsall created the first high-brightness, high-efficiency LEDs for optical fiber telecommunications by inventing new semiconductor materials specifically adapted to optical fiber transmission wavelengths. The first commercial LEDs were commonly used as replacements for incandescent and neon indicator lamps, and in seven-segment displays, first in expensive equipment such as laboratory and electronics test equipment, then later in such appliances as TVs, radios, telephones, calculators, as well as watches (see list of signal uses).


title: "Light-emitting diode" content: Until 1968, visible and infrared LEDs were extremely costly, in the order of US$200 per unit, and so had little practical use. The Monsanto Company was the first organization to mass-produce visible LEDs, using gallium arsenide phosphide (GaAsP) in 1968 to produce red LEDs suitable for indicators. Hewlett-Packard (HP) introduced LEDs in 1968, initially using GaAsP supplied by Monsanto. These red LEDs were bright enough only for use as indicators, as the light output was not enough to illuminate an area. Readouts in calculators were so small that plastic lenses were built over each digit to make them legible. Later,


title: "Light-emitting diode" content: other colors became widely available and appeared in appliances and equipment. In the 1970s commercially successful LED devices at less than five cents each were produced by Fairchild Optoelectronics. These devices employed compound semiconductor chips fabricated with the planar process invented by Dr. Jean Hoerni at Fairchild Semiconductor. The combination of planar processing for chip fabrication and innovative packaging methods enabled the team at Fairchild led by optoelectronics pioneer Thomas Brandt to achieve the needed cost reductions. LED producers continue to use these methods. Most LEDs were made in the very common 5 mm T1¾ and 3 mm T1 packages,


title: "Light-emitting diode" content: but with rising power output, it has grown increasingly necessary to shed excess heat to maintain reliability, so more complex packages have been adapted for efficient heat dissipation. Packages for state-of-the-art high-power LEDs bear little resemblance to early LEDs. Blue LEDs were first developed by Herbert Paul Maruska at RCA in 1972 using gallium nitride (GaN) on a sapphire substrate. SiC types were first commercially sold in the United States by Cree in 1989. However, neither of these initial blue LEDs were very bright. The first high-brightness blue LED was demonstrated by Shuji Nakamura of Nichia Corporation in 1994 and


title: "Light-emitting diode" content: was based on InGaN. In parallel, Isamu Akasaki and Hiroshi Amano in Nagoya were working on developing the important GaN nucleation on sapphire substrates and the demonstration of p-type doping of GaN. Nakamura, Akasaki, and Amano were awarded the 2014 Nobel prize in physics for their work. In 1995, Alberto Barbieri at the Cardiff University Laboratory (GB) investigated the efficiency and reliability of high-brightness LEDs and demonstrated a "transparent contact" LED using indium tin oxide (ITO) on (AlGaInP/GaAs). In 2001 and 2002, processes for growing gallium nitride (GaN) LEDs on silicon were successfully demonstrated. In January 2012, Osram demonstrated high-power


title: "Light-emitting diode" content: InGaN LEDs grown on silicon substrates commercially, and GaN-on-silicon LEDs are in production at Plessey Semiconductors. As of 2017, some manufacturers are using SiC as the substrate for LED production, but sapphire is more common, as it has the most similar properties to that of gallium nitride, reducing the need for patterning the sapphire wafer (patterned wafers are known as epi wafers). Samsung, the University of Cambridge, and Toshiba are performing research into GaN on Si LEDs. Toshiba has stopped research, possibly due to low yields. Some opt towards epitaxy, which is difficult on silicon, while others, like the University


title: "Light-emitting diode" content: of Cambridge, opt towards a multi-layer structure, in order to reduce (crystal) lattice mismatch and different thermal expansion ratios, in order to avoid cracking of the LED chip at high temperatures (e.g. during manufacturing), reduce heat generation and increase luminous efficiency. Epitaxy (or patterned sapphire) can be carried out with nanoimprint lithography. Even though white light can be created using individual red, green and blue LEDs, perhaps using a single SMD (Surface Mount Device) or through-hole RGB LED, this setup results in poor color rendering or CRI, due to the fact that virtually only 3 wavelengths of light are being


title: "Light-emitting diode" content: emitted, so the attainment of high efficiency in blue LEDs was quickly followed by the development of the first white LED. In this device a :Ce (known as "YAG") cerium doped phosphor coating on the emitter absorbs some of the blue emission and produces yellow light through fluorescence. The combination of that yellow with remaining blue light appears white to the eye. However, using different phosphors (fluorescent materials) it also became possible to instead produce green and red light through fluorescence. The resulting mixture of red, green and blue is not only perceived by humans as white light but is


title: "Light-emitting diode" content: superior for illumination in terms of color rendering, whereas one cannot appreciate the color of red or green objects illuminated only by the yellow (and remaining blue) wavelengths from the YAG phosphor. The first white LEDs were expensive and inefficient. However, the light output of LEDs has increased exponentially, with a doubling occurring approximately every 36 months since the 1960s (similar to Moore's law). The latest research and development has been propagated by Japanese manufacturers such as Panasonic, Nichia, etc. and later by Korean and Chinese factories and investment such as: Samsung, Solstice, Kingsun, and countless others. This trend is


title: "Light-emitting diode" content: generally attributed to the parallel development of other semiconductor technologies and advances in optics and materials science and has been called Haitz's law after Dr. Roland Haitz. Light output and efficiency of blue and near-ultraviolet LEDs rose as the cost of reliable devices fell. This led to relatively high-power white-light LEDs for illumination, which are replacing incandescent and fluorescent lighting. Experimental white LEDs have been demonstrated to produce 303 lumens per watt of electricity (lm/w); some can last up to 100,000 hours. However, commercially available LEDs have an efficiency of up to 223 lm/w. Compared to incandescent bulbs, this is


title: "Light-emitting diode" content: not only a huge increase in electrical efficiency but – over time – a similar or lower cost per bulb. The LED chip is encapsulated inside a small, plastic, white mold. It can be encapsulated using resin, silicone, or epoxy containing (powdered) Cerium doped YAG phosphor. After allowing the solvents to evaporate, the LEDs are often tested, and placed on tapes for SMT placement equipment for use in LED light bulb production. Encapsulation is performed after probing, dicing, die transfer from wafer to package, and wire bonding or flip chip mounting, perhaps using Indium tin oxide, a transparent electrical conductor.


title: "Light-emitting diode" content: In this case, the bond wire(s) are attached to the ITO film that has been deposited in the LEDs. The YAG phosphor in the LED's encapsulation compound is why white LEDs look yellow when off. Some LED light bulbs use a single plastic cover with YAG phosphor (remote phosphor) for several blue LEDs instead of using a diffuser and single chip white LEDs. Remote phosphor LED light bulbs may have behind the plastic cover a white plastic reflector. Others shape the remote phosphor as a dome, or sphere, and place it atop a single PCB containing blue LEDs; this assembly


title: "Light-emitting diode" content: may be behind a frosted glass or plastic cover. The PCB is often installed atop a pillar, which is lined with white plastic. A p–n junction can convert absorbed light energy into a proportional electric current. The same process is reversed here (i.e. the p–n junction emits light when electrical energy is applied to it). This phenomenon is generally called electroluminescence, which can be defined as the emission of light from a semiconductor under the influence of an electric field. The charge carriers recombine in a forward-biased p–n junction as the electrons cross from the n-region and recombine with the


title: "Light-emitting diode" content: holes existing in the p-region. Free electrons are in the conduction band of energy levels, while holes are in the valence energy band. Thus the energy level of the holes is lower than the energy levels of the electrons. Some portion of the energy must be dissipated to recombine the electrons and the holes. This energy is emitted in the form of heat and light. The electrons dissipate energy in the form of heat for silicon and germanium diodes, but in gallium arsenide phosphide (GaAsP) and gallium phosphide (GaP) semiconductors, the electrons dissipate energy by emitting photons. If the semiconductor


title: "Light-emitting diode" content: is translucent, the junction becomes the source of light as it is emitted, thus becoming a light-emitting diode. However, when the junction is reversely biased, the LED produces no light, and if the potential is great enough, the device is damaged. The LED consists of a chip of semiconducting material doped with impurities to create a "p-n junction". As in other diodes, current flows easily from the p-side, or anode, to the n-side, or cathode, but not in the reverse direction. Charge-carriers—electrons and holes—flow into the junction from electrodes with different voltages. When an electron meets a hole, it falls


title: "Light-emitting diode" content: into a lower energy level and releases energy in the form of a photon. The wavelength of the light emitted, and thus its color, depends on the band gap energy of the materials forming the "p-n junction". In silicon or germanium diodes, the electrons and holes usually recombine by a "non-radiative transition", which produces no optical emission, because these are indirect band gap materials. The materials used for the LED have a direct band gap with energies corresponding to near-infrared, visible, or near-ultraviolet light. LED development began with infrared and red devices made with gallium arsenide. Advances in materials science


title: "Light-emitting diode" content: have enabled making devices with ever-shorter wavelengths, emitting light in a variety of colors. LEDs are usually built on an n-type substrate, with an electrode attached to the p-type layer deposited on its surface. P-type substrates, while less common, occur as well. Many commercial LEDs, especially GaN/InGaN, also use sapphire substrate. Bare uncoated semiconductors such as silicon exhibit a very high refractive index relative to open air, which prevents passage of photons arriving at sharp angles relative to the air-contacting surface of the semiconductor due to total internal reflection. This property affects both the light-emission efficiency of LEDs as well


title: "Light-emitting diode" content: as the light-absorption efficiency of photovoltaic cells. The refractive index of silicon is set at 3.96 (at 590 nm), while air's refractive index is set at 1.0002926. In general, a flat-surface uncoated LED semiconductor chip emits light only perpendicular to the semiconductor's surface, and a few degrees to the side, in a cone shape referred to as the "light cone", "cone of light", or the "escape cone". The maximum angle of incidence is referred to as the critical angle. When the critical angle is exceeded, photons no longer escape the semiconductor but are, instead, reflected internally inside the semiconductor crystal


title: "Light-emitting diode" content: as if it were a mirror. Internal reflections can escape through other crystalline faces if the incidence angle is low enough and the crystal is sufficiently transparent to not re-absorb the photon emission. But for a simple square LED with 90-degree angled surfaces on all sides, the faces all act as equal angle mirrors. In this case, most of the light can not escape and is lost as waste heat in the crystal. A convoluted chip surface with angled facets similar to a jewel or fresnel lens can increase light output by distributing light perpendicular to the chip surface and


title: "Light-emitting diode" content: far to the sides of the photon emission point. The ideal shape of a semiconductor with maximum light output would be a microsphere with the photon emission occurring at the exact center, with electrodes penetrating to the center to contact at the emission point. All light rays emanating from the center would be perpendicular to the entire surface of the sphere, resulting in no internal reflections. A hemispherical semiconductor would also work, with the flat back-surface serving as a mirror to back-scattered photons. After the doping of the wafer, it is usually cut apart into individual dies. Each die is


title: "Light-emitting diode" content: commonly called a chip. Many LED semiconductor chips are encapsulated or potted in clear or colored molded solid plastic. The plastic encapsulation has three purposes: The third feature helps to boost the light emission from the semiconductor by acting as a diffusing lens, emitting light at a much higher angle of incidence from the light cone than the bare chip would alone. Typical indicator LEDs are designed to operate with no more than 30–60 milliwatts (mW) of electrical power. Around 1999, Philips Lumileds introduced power LEDs capable of continuous use at one watt. These LEDs used much larger semiconductor die


title: "Light-emitting diode" content: sizes to handle the large power inputs. Also, the semiconductor dies were mounted onto metal slugs to allow for greater heat dissipation from the LED die. One of the key advantages of LED-based lighting sources is high luminous efficacy. White LEDs quickly matched and overtook the efficacy of standard incandescent lighting systems. In 2002, Lumileds made five-watt LEDs available with luminous efficacy of 18–22 lumens per watt (lm/W). For comparison, a conventional incandescent light bulb of 60–100 watts emits around 15 lm/W, and standard fluorescent lights emit up to 100 lm/W. , Philips had achieved the following efficacies for each


title: "Light-emitting diode" content: color. The efficiency values show the physics – light power out per electrical power in. The lumen-per-watt efficacy value includes characteristics of the human eye and is derived using the luminosity function. In September 2003, a new type of blue LED was demonstrated by Cree. This produced a commercially packaged white light giving 65 lm/W at 20 mA, becoming the brightest white LED commercially available at the time, and more than four times as efficient as standard incandescents. In 2006, they demonstrated a prototype with a record white LED luminous efficacy of 131 lm/W at 20 mA. Nichia Corporation has


title: "Light-emitting diode" content: developed a white LED with luminous efficacy of 150 lm/W at a forward current of 20 mA. Cree's XLamp XM-L LEDs, commercially available in 2011, produce 100 lm/W at their full power of 10 W, and up to 160 lm/W at around 2 W input power. In 2012, Cree announced a white LED giving 254 lm/W, and 303 lm/W in March 2014. Practical general lighting needs high-power LEDs, of one watt or more. Typical operating currents for such devices begin at 350 mA. These efficiencies are for the light-emitting diode only, held at low temperature in a lab. Since LEDs


title: "Light-emitting diode" content: installed in real fixtures operate at higher temperature and with driver losses, real-world efficiencies are much lower. United States Department of Energy (DOE) testing of commercial LED lamps designed to replace incandescent lamps or CFLs showed that average efficacy was still about 46 lm/W in 2009 (tested performance ranged from 17 lm/W to 79 lm/W). Efficiency droop is the decrease in luminous efficiency of LEDs as the electric current increases above tens of milliamperes. This effect was initially thought related to elevated temperatures. Scientists proved the opposite is true: though the life of an LED is shortened, the efficiency droop


title: "Light-emitting diode" content: is less severe at elevated temperatures. The mechanism causing efficiency droop was identified in 2007 as Auger recombination, which was taken with mixed reaction. In 2013, a study confirmed Auger recombination as the cause of efficiency droop. In addition to being less efficient, operating LEDs at higher electric currents creates higher heat levels, which can compromise LED lifetime. Because of this increased heat at higher currents, high-brightness LEDs have an industry standard of operating at only 350 mA, which is a compromise between light output, efficiency, and longevity. Instead of increasing current levels, luminance is usually increased by combining multiple


title: "Light-emitting diode" content: LEDs in one bulb. Solving the problem of efficiency droop would mean that household LED light bulbs would need fewer LEDs, which would significantly reduce costs. Researchers at the U.S. Naval Research Laboratory have found a way to lessen the efficiency droop. They found that the droop arises from non-radiative Auger recombination of the injected carriers. They created quantum wells with a soft confinement potential to lessen the non-radiative Auger processes. Researchers at Taiwan National Central University and Epistar Corp are developing a way to lessen the efficiency droop by using ceramic aluminium nitride (AlN) substrates, which are more thermally


title: "Light-emitting diode" content: conductive than the commercially used sapphire. The higher thermal conductivity reduces self-heating effects. Solid-state devices such as LEDs are subject to very limited wear and tear if operated at low currents and at low temperatures. Typical lifetimes quoted are 25,000 to 100,000 hours, but heat and current settings can extend or shorten this time significantly. One way to cool down the LED and use the energy efficiently, is to blink the LED in order to gain biomass for example in microalgae cultivation. It is important to note that these projections are based on a standard test that may not accelerate


title: "Light-emitting diode" content: all the potential mechanisms that can induce failures in LEDs. The most common symptom of LED (and diode laser) failure is the gradual lowering of light output and loss of efficiency. Sudden failures, although rare, can also occur. Early red LEDs were notable for their short service life. With the development of high-power LEDs, the devices are subjected to higher junction temperatures and higher current densities than traditional devices. This causes stress on the material and may cause early light-output degradation. To quantify useful lifetime in a standardized manner, some suggest using L70 or L50, which are runtimes (typically in


title: "Light-emitting diode" content: thousands of hours) at which a given LED reaches 70% and 50% of initial light output, respectively. Whereas in most previous sources of light (incandescent lamps, discharge lamps, and those that burn combustible fuel, e.g. candles and oil lamps) the light results from heat, LEDs only operate if they are kept cool enough. The manufacturer commonly specifies a maximum junction temperature of 125 or 150 °C, and lower temperatures are advisable in the interests of long life. At these temperatures, relatively little heat is lost by radiation, which means that the light beam generated by an LED is cool. The


title: "Light-emitting diode" content: waste heat in a high-power LED (which as of 2015 can be less than half the power that it consumes) is conveyed by conduction through the substrate and package of the LED to a heat sink, which gives up the heat to the ambient air by convection. Careful thermal design is, therefore, essential, taking into account the thermal resistances of the LED’s package, the heat sink and the interface between the two. Medium-power LEDs are often designed to solder directly to a printed circuit board that contains a thermally conductive metal layer. (Often, it is a PCB with a white


title: "Light-emitting diode" content: solder mask (white pcb) and a ~1mm thick aluminum backing.) High-power LEDs are packaged in large-area ceramic packages that attach to a metal heat sink—the interface being a material with high thermal conductivity (thermal grease, phase-change material, thermally conductive pad, or thermal adhesive). If an LED-based lamp is installed in an unventilated luminaire, or a luminaire is located in an environment that does not have free air circulation, the LED is likely to overheat, resulting in reduced life or early catastrophic failure. Thermal design is often based on an ambient temperature of . LEDs used in outdoor applications, such as


title: "Light-emitting diode" content: traffic signals or in-pavement signal lights, and in climates where the temperature within the light fixture becomes very high, could experience reduced output or even failure. Since LED efficacy is higher at low temperatures, LED technology is well suited for supermarket freezer lighting. Because LEDs produce less waste heat than incandescent lamps, freezer tube lighting use can save on refrigeration costs as well. However, they may be more susceptible to frost and snow buildup than incandescent lamps, so some LED lighting systems have been designed with an added heating circuit. Additionally, research has developed heat sink technologies that transfer heat


title: "Light-emitting diode" content: produced within the junction to appropriate areas of the light fixture. Conventional LEDs are made from a variety of inorganic semiconductor materials. The following table shows the available colors with wavelength range, voltage drop, and material: The first blue-violet LED using magnesium-doped gallium nitride was made at Stanford University in 1972 by Herb Maruska and Wally Rhines, doctoral students in materials science and engineering. At the time Maruska was on leave from RCA Laboratories, where he collaborated with Jacques Pankove on related work. In 1971, the year after Maruska left for Stanford, his RCA colleagues Pankove and Ed Miller demonstrated


title: "Light-emitting diode" content: the first blue electroluminescence from zinc-doped gallium nitride, though the subsequent device Pankove and Miller built, the first actual gallium nitride light-emitting diode, emitted green light. In 1974 the U.S. Patent Office awarded Maruska, Rhines and Stanford professor David Stevenson a patent for their work in 1972 (U.S. Patent US3819974 A) and today, magnesium-doping of gallium nitride remains the basis for all commercial blue LEDs and laser diodes. In the early 1970s, these devices were too dim for practical use, and research into gallium nitride devices slowed. In August 1989, Cree introduced the first commercially available blue LED based on


title: "Light-emitting diode" content: the indirect bandgap semiconductor, silicon carbide (SiC). SiC LEDs had very low efficiency, no more than about 0.03%, but did emit in the blue portion of the visible light spectrum. In the late 1980s, key breakthroughs in GaN epitaxial growth and p-type doping ushered in the modern era of GaN-based optoelectronic devices. Building upon this foundation, Theodore Moustakas at Boston University patented a method for producing high-brightness blue LEDs using a new two-step process. Two years later, in 1993, high-brightness blue LEDs were demonstrated again by Shuji Nakamura of Nichia Corporation using a gallium nitride growth process similar to Moustakas's.


title: "Light-emitting diode" content: Both Moustakas and Nakamura were issued separate patents, which confused the issue of who was the original inventor (partly because although Moustakas invented his first, Nakamura filed first). This new development revolutionized LED lighting, making high-power blue light sources practical, leading to the development of technologies like Blu-ray, as well as allowing the bright high-resolution screens of modern tablets and phones. Nakamura was awarded the 2006 Millennium Technology Prize for his invention. Nakamura, Hiroshi Amano and Isamu Akasaki were awarded the Nobel Prize in Physics in 2014 for the invention of the blue LED. In 2015, a US court ruled


title: "Light-emitting diode" content: that three companies (i.e. the litigants who had not previously settled out of court) that had licensed Nakamura's patents for production in the United States had infringed Moustakas's prior patent, and ordered them to pay licensing fees of not less than 13 million USD. By the late 1990s, blue LEDs became widely available. They have an active region consisting of one or more InGaN quantum wells sandwiched between thicker layers of GaN, called cladding layers. By varying the relative In/Ga fraction in the InGaN quantum wells, the light emission can in theory be varied from violet to amber. Aluminium gallium


title: "Light-emitting diode" content: nitride (AlGaN) of varying Al/Ga fraction can be used to manufacture the cladding and quantum well layers for ultraviolet LEDs, but these devices have not yet reached the level of efficiency and technological maturity of InGaN/GaN blue/green devices. If un-alloyed GaN is used in this case to form the active quantum well layers, the device emits near-ultraviolet light with a peak wavelength centred around 365 nm. Green LEDs manufactured from the InGaN/GaN system are far more efficient and brighter than green LEDs produced with non-nitride material systems, but practical devices still exhibit efficiency too low for high-brightness applications. With nitrides


title: "Light-emitting diode" content: containing aluminium, most often AlGaN and AlGaInN, even shorter wavelengths are achievable. Ultraviolet LEDs in a range of wavelengths are becoming available on the market. Near-UV emitters at wavelengths around 375–395 nm are already cheap and often encountered, for example, as black light lamp replacements for inspection of anti-counterfeiting UV watermarks in some documents and paper currencies. Shorter-wavelength diodes, while substantially more expensive, are commercially available for wavelengths down to 240 nm. As the photosensitivity of microorganisms approximately matches the absorption spectrum of DNA, with a peak at about 260 nm, UV LED emitting at 250–270 nm are expected in


title: "Light-emitting diode" content: prospective disinfection and sterilization devices. Recent research has shown that commercially available UVA LEDs (365 nm) are already effective disinfection and sterilization devices. UV-C wavelengths were obtained in laboratories using aluminium nitride (210 nm), boron nitride (215 nm) and diamond (235 nm). RGB LEDs consist of one red, one green, and one blue LED. By independently adjusting each of the three, RGB LEDs are capable of producing a wide color gamut. Unlike dedicated-color LEDs, however, these obviously do not produce pure wavelengths. Moreover, such modules as commercially available are often not optimized for smooth color mixing. There are two primary


title: "Light-emitting diode" content: ways of producing white light-emitting diodes (WLEDs), LEDs that generate high-intensity white light. One is to use individual LEDs that emit three primary colors—red, green, and blue—and then mix all the colors to form white light. The other is to use a phosphor material to convert monochromatic light from a blue or UV LED to broad-spectrum white light, much in the same way a fluorescent light bulb works. The 'whiteness' of the light produced is essentially engineered to suit the human eye. The yellow phosphor in LEDs is cerium-doped YAG crystal, in powder form and may be suspended in plastic,


title: "Light-emitting diode" content: epoxy, synthetic rubber or silicone. Touching bare LEDs using synthetic rubber or silicone can damage the delicate wire bonds from LED to package or the LED itself, so they may be protected by a plastic or glass cover, such as in the LED flash in smartphones. It is this YAG phosphor which causes white LEDs without diffusers (such as those used in LED lamps and bulbs) to look yellow when off. There are three main methods of mixing colors to produce white light from an LED: Because of metamerism, it is possible to have quite different spectra that appear white.


title: "Light-emitting diode" content: However, the appearance of objects illuminated by that light may vary as the spectrum varies; this is the issue of color rendition, quite separate from color temperature, where a really orange or cyan object could appear with the wrong color and much darker as the LED or phosphor does not emit the wavelength it reflects. The best color rendition CFL and LEDs use a mix of phosphors, resulting in less efficiency but better quality of light. Though incandescent halogen lamps have a more orange color temperature, they are still the best easily available artificial light sources in terms of color


title: "Light-emitting diode" content: rendition. White light can be formed by mixing differently colored lights; the most common method is to use red, green, and blue (RGB). Hence the method is called multicolor white LEDs (sometimes referred to as RGB LEDs). Because these need electronic circuits to control the blending and diffusion of different colors, and because the individual color LEDs typically have slightly different emission patterns (leading to variation of the color depending on direction) even if they are made as a single unit, these are seldom used to produce white lighting. Nonetheless, this method has many applications because of the flexibility of


title: "Light-emitting diode" content: mixing different colors, and in principle, this mechanism also has higher quantum efficiency in producing white light. There are several types of multicolor white LEDs: di-, tri-, and tetrachromatic white LEDs. Several key factors that play among these different methods include color stability, color rendering capability, and luminous efficacy. Often, higher efficiency means lower color rendering, presenting a trade-off between the luminous efficacy and color rendering. For example, the dichromatic white LEDs have the best luminous efficacy (120 lm/W), but the lowest color rendering capability. However, although tetrachromatic white LEDs have excellent color rendering capability, they often have poor luminous


title: "Light-emitting diode" content: efficacy. Trichromatic white LEDs are in between, having both good luminous efficacy (>70 lm/W) and fair color rendering capability. One of the challenges is the development of more efficient green LEDs. The theoretical maximum for green LEDs is 683 lumens per watt but as of 2010 few green LEDs exceed even 100 lumens per watt. The blue and red LEDs approach their theoretical limits. Multicolor LEDs offer not merely another means to form white light but a new means to form light of different colors. Most perceivable colors can be formed by mixing different amounts of three primary colors. This


title: "Light-emitting diode" content: allows precise dynamic color control. As more effort is devoted to investigating this method, multicolor LEDs should have profound influence on the fundamental method that we use to produce and control light color. However, before this type of LED can play a role on the market, several technical problems must be solved. These include that this type of LED's emission power decays exponentially with rising temperature, resulting in a substantial change in color stability. Such problems inhibit and may preclude industrial use. Thus, many new package designs aimed at solving this problem have been proposed and their results are now


title: "Light-emitting diode" content: being reproduced by researchers and scientists. However multicolor LEDs without phosphors can never provide good quality lighting because each LED is a narrow band source (see graph). LEDs without phosphor while a poorer solution for general lighting are the best solution for displays, either backlight of LCD, or direct LED based pixels. Correlated color temperature (CCT) dimming for LED technology is regarded as a difficult task since LED binning, age and temperature drift effects of LEDs change the actual color value output. Feedback loop systems are used for example with color sensors, to actively monitor and control the color output


title: "Light-emitting diode" content: of multiple color mixing LEDs. This method involves coating LEDs of one color (mostly blue LEDs made of InGaN) with phosphors of different colors to form white light; the resultant LEDs are called phosphor-based or phosphor-converted white LEDs (pcLEDs). A fraction of the blue light undergoes the Stokes shift, which transforms it from shorter wavelengths to longer. Depending on the original LED's color, various color phosphors are used. Using several phosphor layers of distinct colors broadens the emitted spectrum, effectively raising the color rendering index (CRI). Phosphor-based LEDs have efficiency losses due to heat loss from the Stokes shift and


title: "Light-emitting diode" content: also other phosphor-related issues. Their luminous efficacies compared to normal LEDs depend on the spectral distribution of the resultant light output and the original wavelength of the LED itself. For example, the luminous efficacy of a typical YAG yellow phosphor based white LED ranges from 3 to 5 times the luminous efficacy of the original blue LED because of the human eye's greater sensitivity to yellow than to blue (as modeled in the luminosity function). Due to the simplicity of manufacturing, the phosphor method is still the most popular method for making high-intensity white LEDs. The design and production of


title: "Light-emitting diode" content: a light source or light fixture using a monochrome emitter with phosphor conversion is simpler and cheaper than a complex RGB system, and the majority of high-intensity white LEDs presently on the market are manufactured using phosphor light conversion. Among the challenges being faced to improve the efficiency of LED-based white light sources is the development of more efficient phosphors. As of 2010, the most efficient yellow phosphor is still the YAG phosphor, with less than 10% Stokes shift loss. Losses attributable to internal optical losses due to re-absorption in the LED chip and in the LED packaging itself account


title: "Light-emitting diode" content: typically for another 10% to 30% of efficiency loss. Currently, in the area of phosphor LED development, much effort is being spent on optimizing these devices to higher light output and higher operation temperatures. For instance, the efficiency can be raised by adapting better package design or by using a more suitable type of phosphor. Conformal coating process is frequently used to address the issue of varying phosphor thickness. Some phosphor-based white LEDs encapsulate InGaN blue LEDs inside phosphor-coated epoxy. Alternatively, the LED might be paired with a remote phosphor, a preformed polycarbonate piece coated with the phosphor material. Remote


title: "Light-emitting diode" content: phosphors provide more diffuse light, which is desirable for many applications. Remote phosphor designs are also more tolerant of variations in the LED emissions spectrum. A common yellow phosphor material is cerium-doped yttrium aluminium garnet (Ce:YAG). White LEDs can also be made by coating near-ultraviolet (NUV) LEDs with a mixture of high-efficiency europium-based phosphors that emit red and blue, plus copper and aluminium-doped zinc sulfide (ZnS:Cu, Al) that emits green. This is a method analogous to the way fluorescent lamps work. This method is less efficient than blue LEDs with YAG:Ce phosphor, as the Stokes shift is larger, so more


title: "Light-emitting diode" content: energy is converted to heat, but yields light with better spectral characteristics, which render color better. Due to the higher radiative output of the ultraviolet LEDs than of the blue ones, both methods offer comparable brightness. A concern is that UV light may leak from a malfunctioning light source and cause harm to human eyes or skin. Another method used to produce experimental white light LEDs used no phosphors at all and was based on homoepitaxially grown zinc selenide (ZnSe) on a ZnSe substrate that simultaneously emitted blue light from its active region and yellow light from the substrate. A


title: "Light-emitting diode" content: new style of wafers composed of gallium-nitride-on-silicon (GaN-on-Si) is being used to produce white LEDs using 200-mm silicon wafers. This avoids the typical costly sapphire substrate in relatively small 100- or 150-mm wafer sizes. The sapphire apparatus must be coupled with a mirror-like collector to reflect light that would otherwise be wasted. It is predicted that by 2020, 40% of all GaN LEDs will be made with GaN-on-Si. Manufacturing large sapphire material is difficult, while large silicon material is cheaper and more abundant. LED companies shifting from using sapphire to silicon should be a minimal investment. In an organic light-emitting


title: "Light-emitting diode" content: diode (OLED), the electroluminescent material composing the emissive layer of the diode is an organic compound. The organic material is electrically conductive due to the delocalization of pi electrons caused by conjugation over all or part of the molecule, and the material therefore functions as an organic semiconductor. The organic materials can be small organic molecules in a crystalline phase, or polymers. The potential advantages of OLEDs include thin, low-cost displays with a low driving voltage, wide viewing angle, and high contrast and color gamut. Polymer LEDs have the added benefit of printable and flexible displays. OLEDs have been used


title: "Light-emitting diode" content: to make visual displays for portable electronic devices such as cellphones, digital cameras, and MP3 players while possible future uses include lighting and televisions. Quantum dots (QD) are semiconductor nanocrystals with optical properties that let their emission color be tuned from the visible into the infrared spectrum. This allows quantum dot LEDs to create almost any color on the CIE diagram. This provides more color options and better color rendering than white LEDs since the emission spectrum is much narrower, characteristic of quantum confined states. There are two types of schemes for QD excitation. One uses photo excitation with a


title: "Light-emitting diode" content: primary light source LED (typically blue or UV LEDs are used). The other is direct electrical excitation first demonstrated by Alivisatos et al. One example of the photo-excitation scheme is a method developed by Michael Bowers, at Vanderbilt University in Nashville, involving coating a blue LED with quantum dots that glow white in response to the blue light from the LED. This method emits a warm, yellowish-white light similar to that made by incandescent light bulbs. Quantum dots are also being considered for use in white light-emitting diodes in liquid crystal display (LCD) televisions. In February 2011 scientists at PlasmaChem


title: "Light-emitting diode" content: GmbH were able to synthesize quantum dots for LED applications and build a light converter on their basis, which was able to efficiently convert light from blue to any other color for many hundred hours. Such QDs can be used to emit visible or near infrared light of any wavelength being excited by light with a shorter wavelength. The structure of QD-LEDs used for the electrical-excitation scheme is similar to basic design of OLEDs. A layer of quantum dots is sandwiched between layers of electron-transporting and hole-transporting materials. An applied electric field causes electrons and holes to move into the


title: "Light-emitting diode" content: quantum dot layer and recombine forming an exciton that excites a QD. This scheme is commonly studied for quantum dot display. The tunability of emission wavelengths and narrow bandwidth is also beneficial as excitation sources for fluorescence imaging. Fluorescence near-field scanning optical microscopy (NSOM) utilizing an integrated QD-LED has been demonstrated. In February 2008, a luminous efficacy of 300 lumens of visible light per watt of radiation (not per electrical watt) and warm-light emission was achieved by using nanocrystals. The main types of LEDs are miniature, high-power devices, and custom designs such as alphanumeric or multicolor. These are mostly single-die


title: "Light-emitting diode" content: LEDs used as indicators, and they come in various sizes from 2 mm to 8 mm, through-hole and surface mount packages. They usually do not use a separate heat sink. Typical current ratings range from around 1 mA to above 20 mA. The small size sets a natural upper boundary on power consumption due to heat caused by the high current density and need for a heat sink. Often daisy chained as used in LED tapes. Common package shapes include round, with a domed or flat top, rectangular with a flat top (as used in bar-graph displays), and triangular or


title: "Light-emitting diode" content: square with a flat top. The encapsulation may also be clear or tinted to improve contrast and viewing angle. Researchers at the University of Washington have invented the thinnest LED. It is made of two-dimensional (2-D) flexible materials. It is three atoms thick, which is 10 to 20 times thinner than three-dimensional (3-D) LEDs and is also 10,000 times smaller than the thickness of a human hair. These 2-D LEDs are going to make it possible to create smaller, more energy-efficient lighting, optical communication and nano lasers. There are three main categories of miniature single die LEDs: 5 V and


title: "Light-emitting diode" content: 12 V LEDs are ordinary miniature LEDs that incorporate a suitable series resistor for direct connection to a 5 V or 12 V supply. High-power LEDs (HP-LEDs) or high-output LEDs (HO-LEDs) can be driven at currents from hundreds of mA to more than an ampere, compared with the tens of mA for other LEDs. Some can emit over a thousand lumens. LED power densities up to 300 W/cm have been achieved. Since overheating is destructive, the HP-LEDs must be mounted on a heat sink to allow for heat dissipation. If the heat from an HP-LED is not removed, the device


title: "Light-emitting diode" content: fails in seconds. One HP-LED can often replace an incandescent bulb in a flashlight, or be set in an array to form a powerful LED lamp. Some well-known HP-LEDs in this category are the Nichia 19 series, Lumileds Rebel Led, Osram Opto Semiconductors Golden Dragon, and Cree X-lamp. As of September 2009, some HP-LEDs manufactured by Cree now exceed 105 lm/W. Examples for Haitz's law—which predicts an exponential rise in light output and efficacy of LEDs over time—are the CREE XP-G series LED, which achieved 105 lm/W in 2009 and the Nichia 19 series with a typical efficacy of 140


title: "Light-emitting diode" content: lm/W, released in 2010. LEDs developed by Seoul Semiconductor can operate on AC power without a DC converter. For each half-cycle, part of the LED emits light and part is dark, and this is reversed during the next half-cycle. The efficacy of this type of HP-LED is typically 40 lm/W. A large number of LED elements in series may be able to operate directly from line voltage. In 2009, Seoul Semiconductor released a high DC voltage LED, named as 'Acrich MJT', capable of being driven from AC power with a simple controlling circuit. The low-power dissipation of these LEDs affords


title: "Light-emitting diode" content: them more flexibility than the original AC LED design. Flashing LEDs are used as attention seeking indicators without requiring external electronics. Flashing LEDs resemble standard LEDs but they contain an integrated multivibrator circuit that causes the LED to flash with a typical period of one second. In diffused lens LEDs, this circuit is visible as a small black dot. Most flashing LEDs emit light of one color, but more sophisticated devices can flash between multiple colors and even fade through a color sequence using RGB color mixing. Bi-color LEDs contain two different LED emitters in one case. There are two


title: "Light-emitting diode" content: types of these. One type consists of two dies connected to the same two leads antiparallel to each other. Current flow in one direction emits one color, and current in the opposite direction emits the other color. The other type consists of two dies with separate leads for both dies and another lead for common anode or cathode so that they can be controlled independently. The most common bi-color combination is red/traditional green, however, other available combinations include amber/traditional green, red/pure green, red/blue, and blue/pure green. Tri-color LEDs contain three different LED emitters in one case. Each emitter is connected


title: "Light-emitting diode" content: to a separate lead so they can be controlled independently. A four-lead arrangement is typical with one common lead (anode or cathode) and an additional lead for each color. RGB LEDs are tri-color LEDs with red, green, and blue emitters, in general using a four-wire connection with one common lead (anode or cathode). Others, however, have only two leads (positive and negative) and have a built-in electronic control unit. Decorative-multicolor LEDs incorporate several emitters of different colors supplied by only two lead-out wires. Colors are switched internally by varying the supply voltage. Alphanumeric LEDs are available in seven-segment, starburst, and


title: "Light-emitting diode" content: dot-matrix format. Seven-segment displays handle all numbers and a limited set of letters. Starburst displays can display all letters. Dot-matrix displays typically use 5x7 pixels per character. Seven-segment LED displays were in widespread use in the 1970s and 1980s, but rising use of liquid crystal displays, with their lower power needs and greater display flexibility, has reduced the popularity of numeric and alphanumeric LED displays. Digital RGB Addressable LEDs are RGB LEDs that contain their own "smart" control electronics. In addition to power and ground, these provide connections for data-in, data-out, and sometimes a clock or strobe signal. These are


title: "Light-emitting diode" content: connected in a daisy chain, with the data in of the first LED sourced by a microprocessor, which can control the brightness and color of each LED independently of the others. They are used where a combination of maximum control and minimum visible electronics are needed such as strings for Christmas and LED matrices. Some even have refresh rates in the kHz range, allowing for basic video applications. These devices are also known by their part number (WS2812 being the most common) or a brand name such as NeoPixel An LED filament consists of multiple LED chips connected in series


title: "Light-emitting diode" content: on a common longitudinal substrate that forms a thin rod reminiscent of a traditional incandescent filament. These are being used as a low-cost decorative alternative for traditional light bulbs that are being phased out in many countries. The filaments require a rather high voltage to light to nominal brightness, allowing them to work efficiently and simply with mains voltages. Often a simple rectifier and capacitive current limiting are employed to create a low-cost replacement for a traditional light bulb without the complexity of the low voltage, high current converter that single die LEDs need. Usually, they are packaged in a


title: "Light-emitting diode" content: sealed enclosure with a shape similar to lamps they were designed to replace (e.g. a bulb) and filled with inert nitrogen or carbon dioxide gas to remove heat efficiently. The current–voltage characteristic of an LED is similar to other diodes, in that the current is dependent exponentially on the voltage (see Shockley diode equation). This means that a small change in voltage can cause a large change in current. If the applied voltage exceeds the LED's forward voltage drop by a small amount, the current rating may be exceeded by a large amount, potentially damaging or destroying the LED. The


title: "Light-emitting diode" content: typical solution is to use constant-current power supplies to keep the current below the LED's maximum current rating. Since most common power sources (batteries, mains) are constant-voltage sources, most LED fixtures must include a power converter, at least a current-limiting resistor. However, the high resistance of three-volt coin cells combined with the high differential resistance of nitride-based LEDs makes it possible to power such an LED from such a coin cell without an external resistor. As with all diodes, current flows easily from p-type to n-type material. However, no current flows and no light is emitted if a small voltage


title: "Light-emitting diode" content: is applied in the reverse direction. If the reverse voltage grows large enough to exceed the breakdown voltage, a large current flows and the LED may be damaged. If the reverse current is sufficiently limited to avoid damage, the reverse-conducting LED is a useful noise diode. The vast majority of devices containing LEDs are "safe under all conditions of normal use", and so are classified as "Class 1 LED product"/"LED Klasse 1". At present, only a few LEDs—extremely bright LEDs that also have a tightly focused viewing angle of 8° or less—could, in theory, cause temporary blindness, and so are


title: "Light-emitting diode" content: classified as "Class 2". The opinion of the French Agency for Food, Environmental and Occupational Health & Safety (ANSES) of 2010, on the health issues concerning LEDs, suggested banning public use of lamps in the moderate Risk Group 2, especially those with a high blue component, in places frequented by children. In general, laser safety regulations—and the "Class 1", "Class 2", etc. system—also apply to LEDs. While LEDs have the advantage over fluorescent lamps that they do not contain mercury, they may contain other hazardous metals such as lead and arsenic. Regarding the toxicity of LEDs when treated as waste,


title: "Light-emitting diode" content: a study published in 2011 stated: "According to federal standards, LEDs are not hazardous except for low-intensity red LEDs, which leached Pb [lead] at levels exceeding regulatory limits (186 mg/L; regulatory limit: 5). However, according to California regulations, excessive levels of copper (up to 3892 mg/kg; limit: 2500), lead (up to 8103 mg/kg; limit: 1000), nickel (up to 4797 mg/kg; limit: 2000), or silver (up to 721 mg/kg; limit: 500) render all except low-intensity yellow LEDs hazardous." In 2016 a statement of the American Medical Association (AMA) concerning the possible influence of blueish street lighting on the sleep-wake cycle of


title: "Light-emitting diode" content: city-dwellers led to some controversy. So far high-pressure sodium lamps (HPS) with an orange light spectrum were the most efficient light sources commonly used in street-lighting. Now many modern street lamps are equipped with Indium gallium nitride LEDs (InGaN). These are even more efficient and mostly emit blue-rich light with a higher "correlated color temperature (CCT)". Since light with a high CCT resembles daylight it is thought that this might have an effect on the normal circadian physiology by suppressing melatonin production in the human body. There have been no relevant studies as yet and critics claim exposure levels are


title: "Light-emitting diode" content: not high enough to have a noticeable effect. LED uses fall into four major categories: The low energy consumption, low maintenance and small size of LEDs has led to uses as status indicators and displays on a variety of equipment and installations. Large-area LED displays are used as stadium displays, dynamic decorative displays, and dynamic message signs on freeways. Thin, lightweight message displays are used at airports and railway stations, and as destination displays for trains, buses, trams, and ferries. One-color light is well suited for traffic lights and signals, exit signs, emergency vehicle lighting, ships' navigation lights or lanterns


title: "Light-emitting diode" content: (chromacity and luminance standards being set under the Convention on the International Regulations for Preventing Collisions at Sea 1972, Annex I and the CIE) and LED-based Christmas lights. In cold climates, LED traffic lights may remain snow-covered. Red or yellow LEDs are used in indicator and alphanumeric displays in environments where night vision must be retained: aircraft cockpits, submarine and ship bridges, astronomy observatories, and in the field, e.g. night time animal watching and military field use. Because of their long life, fast switching times, and visibility in broad daylight due to their high output and focus, LEDs have been


title: "Light-emitting diode" content: used in brake lights for cars' high-mounted brake lights, trucks, and buses, and in turn signals for some time. However, many vehicles now use LEDs for their rear light clusters. The use in brakes improves safety, due to a great reduction in the time needed to light fully, or faster rise time, up to 0.5 second faster than an incandescent bulb. This gives drivers behind more time to react. In a dual intensity circuit (rear markers and brakes) if the LEDs are not pulsed at a fast enough frequency, they can create a phantom array, where ghost images of the


title: "Light-emitting diode" content: LED appear if the eyes quickly scan across the array. White LED headlamps are beginning to appear. Using LEDs has styling advantages because LEDs can form much thinner lights than incandescent lamps with parabolic reflectors. Due to the relative cheapness of low output LEDs, they are also used in many temporary uses such as glowsticks, throwies, and the photonic textile Lumalive. Artists have also used LEDs for LED art. Weather and all-hazards radio receivers with Specific Area Message Encoding (SAME) have three LEDs: red for warnings, orange for watches, and yellow for advisories and statements whenever issued. With the development


title: "Light-emitting diode" content: of high-efficiency and high-power LEDs, it has become possible to use LEDs in lighting and illumination. To encourage the shift to LED lamps and other high-efficiency lighting, the US Department of Energy has created the L Prize competition. The Philips Lighting North America LED bulb won the first competition on August 3, 2011, after successfully completing 18 months of intensive field, lab, and product testing. LEDs are used as street lights and in other architectural lighting. The mechanical robustness and long lifetime are used in automotive lighting on cars, motorcycles, and bicycle lights. LED light emission may be efficiently controlled


title: "Light-emitting diode" content: by using nonimaging optics principles. LED street lights are employed on poles and in parking garages. In 2007, the Italian village of Torraca was the first place to convert its entire illumination system to LEDs. LEDs are used in aviation lighting. Airbus has used LED lighting in its Airbus A320 Enhanced since 2007, and Boeing uses LED lighting in the 787 and 737 Sky Interior. LEDs are also being used now in airport and heliport lighting. LED airport fixtures currently include medium-intensity runway lights, runway centerline lights, taxiway centerline and edge lights, guidance signs, and obstruction lighting. LEDs are also


title: "Light-emitting diode" content: used as a light source for DLP projectors, and to backlight LCD televisions (referred to as LED TVs) and laptop displays. RGB LEDs raise the color gamut by as much as 45%. Screens for TV and computer displays can be made thinner using LEDs for backlighting. The lack of IR or heat radiation makes LEDs ideal for stage lights using banks of RGB LEDs that can easily change color and decrease heating from traditional stage lighting, as well as medical lighting where IR-radiation can be harmful. In energy conservation, the lower heat output of LEDs also means air conditioning (cooling)


title: "Light-emitting diode" content: systems have less heat in need of disposal. LEDs are small, durable and need little power, so they are used in handheld devices such as flashlights. LED strobe lights or camera flashes operate at a safe, low voltage, instead of the 250+ volts commonly found in xenon flashlamp-based lighting. This is especially useful in cameras on mobile phones, where space is at a premium and bulky voltage-raising circuitry is undesirable. LEDs are used for infrared illumination in night vision uses including security cameras. A ring of LEDs around a video camera, aimed forward into a retroreflective background, allows chroma keying


title: "Light-emitting diode" content: in video productions. LEDs are used in mining operations, as cap lamps to provide light for miners. Research has been done to improve LEDs for mining, to reduce glare and to increase illumination, reducing risk of injury to the miners. LEDs are now used commonly in all market areas from commercial to home use: standard lighting, AV, stage, theatrical, architectural, and public installations, and wherever artificial light is used. LEDs are increasingly finding uses in medical and educational applications, for example as mood enhancement, and new technologies such as AmBX, exploiting LED versatility. NASA has even sponsored research for the


title: "Light-emitting diode" content: use of LEDs to promote health for astronauts. Light can be used to transmit data and analog signals. For example, lighting white LEDs can be used in systems assisting people to navigate in closed spaces while searching necessary rooms or objects. Assistive listening devices in many theaters and similar spaces use arrays of infrared LEDs to send sound to listeners' receivers. Light-emitting diodes (as well as semiconductor lasers) are used to send data over many types of fiber optic cable, from digital audio over TOSLINK cables to the very high bandwidth fiber links that form the Internet backbone. For some


title: "Light-emitting diode" content: time, computers were commonly equipped with IrDA interfaces, which allowed them to send and receive data to nearby machines via infrared. Because LEDs can cycle on and off millions of times per second, very high data bandwidth can be achieved. Efficient lighting is needed for sustainable architecture. In 2009, US Department of Energy testing results on LED lamps showed an average efficacy of 35 lm/W, below that of typical CFLs, and as low as 9 lm/W, worse than standard incandescent bulbs. A typical 13-watt LED lamp emitted 450 to 650 lumens, which is equivalent to a standard 40-watt incandescent bulb.


title: "Light-emitting diode" content: However, as of 2011, there are LED bulbs available as efficient as 150 lm/W and even inexpensive low-end models typically exceed 50 lm/W, so that a 6-watt LED could achieve the same results as a standard 40-watt incandescent bulb. The latter has an expected lifespan of 1,000 hours, whereas an LED can continue to operate with reduced efficiency for more than 50,000 hours. See the chart below for a comparison of common light types: In the US, one kilowatt-hour (3.6 MJ) of electricity currently causes an average of emission. Assuming the average light bulb is on for 10 hours a


title: "Light-emitting diode" content: day, a 40-watt bulb causes of emission per year. The 6-watt LED equivalent only causes of over the same time span. A building’s carbon footprint from lighting can, therefore, be reduced by 85% by exchanging all incandescent bulbs for new LEDs—if a building previously used only incandescent bulbs. In practice, most buildings that use a lot of lighting use fluorescent lighting, which has 22% luminous efficiency compared with 5% for filaments, so changing to LED lighting would still give a 34% reduction in electrical power use and carbon emissions. The reduction in carbon emissions depends on the source of electricity.


title: "Light-emitting diode" content: Nuclear power in the United States produced 19.2% of electricity in 2011, so reducing electricity consumption in the U.S. reduces carbon emissions more than in France (75% nuclear electricity) or Norway (almost entirely hydroelectric). Replacing lights that spend the most time lit results in the most savings, so LED lights in infrequently used locations bring a smaller return on investment. Machine vision systems, also known as Computer vision systems, often require bright and homogeneous illumination, so features of interest are easier to process. LEDs are often used to achieve this type of purpose, and this is likely to remain one


title: "Light-emitting diode" content: of their major uses until their price drops low enough to make signaling and illumination uses more economically feasible. Barcode scanners are the most common example of machine vision applications, and many of those scanners use low-cost products red LEDs instead of laser-based LEDs. Optical computer mice are an example of LEDs in machine vision, as it is used to provide an even light source on the surface for the miniature camera within the mouse. LEDs constitute a nearly ideal light source for machine vision systems for several reasons: The light from LEDs can be modulated very quickly so they


title: "Light-emitting diode" content: are used extensively in optical fiber and free space optics communications. This includes remote controls, such as for TVs, VCRs, and LED Computers, where infrared LEDs are often used. Opto-isolators use an LED combined with a photodiode or phototransistor to provide a signal path with electrical isolation between two circuits. This is especially useful in medical equipment where the signals from a low-voltage sensor circuit (usually battery-powered) in contact with a living organism must be electrically isolated from any possible electrical failure in a recording or monitoring device operating at potentially dangerous voltages. An optoisolator also lets information be transferred


title: "Light-emitting diode" content: between circuits that don't share a common ground potential. Many sensor systems rely on light as the signal source. LEDs are often ideal as a light source due to the requirements of the sensors. LEDs are used as motion sensors, for example in optical computer mice. The Nintendo Wii's sensor bar uses infrared LEDs. Pulse oximeters use them for measuring oxygen saturation. Some flatbed scanners use arrays of RGB LEDs rather than the typical cold-cathode fluorescent lamp as the light source. Having independent control of three illuminated colors allows the scanner to calibrate itself for more accurate color balance, and


title: "Light-emitting diode" content: there is no need for warm-up. Further, its sensors only need be monochromatic, since at any one time the page being scanned is only lit by one color of light. Since LEDs can also be used as photodiodes, they can be used for both photo emission and detection. This could be used, for example, in a touchscreen that registers reflected light from a finger or stylus. Many materials and biological systems are sensitive to, or dependent on, light. Grow lights use LEDs to increase photosynthesis in plants, and bacteria and viruses can be removed from water and other substances using


title: "Light-emitting diode" content: UV LEDs for sterilization. LEDs have also been used as a medium-quality voltage reference in electronic circuits. The forward voltage drop (e.g. about 1.7 V for a normal red LED) can be used instead of a Zener diode in low-voltage regulators. Red LEDs have the flattest I/V curve above the knee. Nitride-based LEDs have a fairly steep I/V curve and are useless for this purpose. Although LED forward voltage is far more current-dependent than a Zener diode, Zener diodes with breakdown voltages below 3 V are not widely available. The progressive miniaturization of low-voltage lighting technology, such as LEDs and


title: "Light-emitting diode" content: OLEDs, suitable to incorporate into low-thickness materials has fostered experimentation in combining light sources and wall covering surfaces for interior walls. The new possibilities offered by these developments have prompted some designers and companies, such as Meystyle, Ingo Maurer, Lomox and Samsung, to research and develop proprietary LED wallpaper technologies, some of which are currently available for commercial purchase. Other solutions mainly exist as prototypes or are in the process of being further refined. Light-emitting diode A light-emitting diode (LED) is a two-lead semiconductor light source. It is a p–n junction diode that emits light when activated. When a suitable


title: Lucifer content: the Etruscan god Tagni, or Dianus (Janus, following the work of folklorist James Frazer in "The Golden Bough"). Lucifer Lucifer ( ; "light-bringer") was a Latin name for the planet Venus as the morning star in the ancient Roman era, and is often used for mythological and religious figures associated with the planet. Due to the unique movements and discontinuous appearances of Venus in the sky, mythology surrounding these figures often involved a fall from the heavens to earth or the underworld. Interpretations of a similar term in the Hebrew Bible, translated in the King James Version as "Lucifer", led


title: Lexus content: marque's German competitors. An annual "December to Remember" campaign featured scenes of family members surprising loved ones with the gift of a new Lexus. The marque returned to the champagne glass theme in a 2006 LS 460 spot showing the sedan maneuvering between two stacks of glasses using its self-parking system, and in a 2010 LFA spot showing its engine sound shattering a glass via resonance frequency. Industry observers have attributed Lexus' early marketing successes to higher levels of perceived quality and lower prices than competitors, which have enabled the marque to attract customers upgrading from mass-market cars. A reputation


title: Lindisfarne content: Lindisfarne The Holy Island of Lindisfarne, also known simply as Holy Island, is a tidal island off the northeast coast of England, which constitutes the civil parish of Holy Island in Northumberland. Holy Island has a recorded history from the 6th century AD; it was an important centre of Celtic Christianity under Saints Aidan of Lindisfarne, Cuthbert, Eadfrith of Lindisfarne and Eadberht of Lindisfarne. After the Viking invasions and the Norman conquest of England, a priory was reestablished. A small castle was built on the island in 1550. The island of Lindisfarne appears under the Old Welsh name "Medcaut" in