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86-506: Lumileds is a lighting company that develops, manufactures, and distributes LEDs , light bulbs , and related products for automotive lighting , general lighting, and specialty lighting. Lumileds operates as a private company, having funds affiliated with Apollo Global Management . Lumileds was formed in November 1999 as a joint venture between Philips Lighting and Agilent Technologies . Upon Philips' acquisition in 2005, Lumileds became

172-563: 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 ,

258-492: A band in the vicinity of 400–790  terahertz . These boundaries are not sharply defined and may vary per individual. Under optimal conditions, these limits of human perception can extend to 310 nm (ultraviolet) and 1100 nm (near infrared). The spectrum does not contain all the colors that the human visual system can distinguish. Unsaturated colors such as pink , or purple variations like magenta , for example, are absent because they can only be made from

344-534: A bid to deleverage and strengthen its balance sheet in effort to emerge from bankruptcy within less than 60 days. Lumileds' other international subsidiaries were not part of the bankruptcy reorganization. 63 days after the company filed for bankruptcy, Lumileds completed its bankruptcy restructuring and exited bankruptcy on November 1, 2022. The company sells products for automotive, illumination and specialty applications, with automotive lighting comprising 60% of its sales in 2015. In architectural lighting they released

430-615: A business unit within Philips Lighting and became known as Philips Lumileds Lighting Company. In March 2015, Lumileds parent company Philips agreed to sell an 80.1 percent stake in the business to the investment fund, Go Scale. In October 2015, Financial Times reported that the Committee on Foreign Investment in the United States (CFIUS) regulatory body may block the $ 2.9B deal owing to fears of Chinese subversion of

516-671: A current source of a battery or a pulse generator and with a comparison to a variant, pure, crystal in 1953. 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

602-486: A ghostly optical afterimage , as did Schopenhauer in On Vision and Colors . Goethe argued that the continuous spectrum was a compound phenomenon. Where Newton narrowed the beam of light to isolate the phenomenon, Goethe observed that a wider aperture produces not a spectrum but rather reddish-yellow and blue-cyan edges with white between them. The spectrum appears only when these edges are close enough to overlap. In

688-554: A glass window or lens to let the light out. Modern indicator LEDs are packed in transparent molded plastic cases, tubular or rectangular in shape, and often tinted to match the device color. Infrared devices may be dyed, to block visible light. More complex packages have been adapted for efficient heat dissipation in high-power LEDs . Surface-mounted LEDs further reduce the package size. LEDs intended for use with fiber optics cables may be provided with an optical connector. The first blue -violet LED, using magnesium-doped gallium nitride

774-449: A hard cutoff, but rather an exponential decay, such that the function's value (or vision sensitivity) at 1,050 nm is about 10 times weaker than at 700 nm; much higher intensity is therefore required to perceive 1,050 nm light than 700 nm light. Under ideal laboratory conditions, subjects may perceive infrared light up to at least 1,064 nm. While 1,050 nm NIR light can evoke red, suggesting direct absorption by

860-1198: A layer of light-emitting phosphor on the semiconductor device. Appearing as practical electronic components in 1962, the earliest LEDs emitted low-intensity infrared (IR) light. Infrared LEDs are used in remote-control circuits, such as those used with a wide variety of consumer electronics. The first visible-light LEDs were of low intensity and limited to red. Early LEDs were often used as indicator lamps, replacing small incandescent bulbs , and in seven-segment displays . Later developments produced LEDs available in visible , ultraviolet (UV), and infrared wavelengths with high, low, or intermediate light output, for instance, white LEDs suitable for room and outdoor lighting. LEDs have also given rise to new types of displays and sensors, while their high switching rates are useful in advanced communications technology with applications as diverse as aviation lighting , fairy lights , strip lights , automotive headlamps , advertising, general lighting , traffic signals , camera flashes, lighted wallpaper , horticultural grow lights , and medical devices. LEDs have many advantages over incandescent light sources, including lower power consumption,

946-568: A longer lifetime, improved physical robustness, smaller sizes, and faster switching. In exchange for these generally favorable attributes, disadvantages of LEDs include electrical limitations to low voltage and generally to DC (not AC) power, the inability to provide steady illumination from a pulsing DC or an AC electrical supply source, and a lesser maximum operating temperature and storage temperature. LEDs are transducers of electricity into light. They operate in reverse of photodiodes , which convert light into electricity. Electroluminescence as

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1032-485: A loudspeaker. Intercepting the beam stopped the music. We had a great deal of fun playing with this setup." 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 signal coupling between

1118-557: A method for producing high-brightness blue LEDs using a new two-step process in 1991. In 2015, a US court ruled that three Taiwanese companies had infringed Moustakas's prior patent, and ordered them to pay licensing fees of not less than US$ 13 million. Two years later, in 1993, high-brightness blue LEDs were demonstrated by Shuji Nakamura of Nichia Corporation using a gallium nitride (GaN) growth process. These LEDs had efficiencies of 10%. In parallel, Isamu Akasaki and Hiroshi Amano of Nagoya University were working on developing

1204-459: A mix of multiple wavelengths. Colors containing only one wavelength are also called pure colors or spectral colors . Visible wavelengths pass largely unattenuated through the Earth's atmosphere via the " optical window " region of the electromagnetic spectrum. An example of this phenomenon is when clean air scatters blue light more than red light, and so the midday sky appears blue (apart from

1290-404: A narrow band of wavelengths ( monochromatic light ) are called pure spectral colors . The various color ranges indicated in the illustration are an approximation: The spectrum is continuous, with no clear boundaries between one color and the next. In the 13th century, Roger Bacon theorized that rainbows were produced by a similar process to the passage of light through glass or crystal. In

1376-523: A phenomenon was discovered in 1907 by the English experimenter Henry Joseph Round of Marconi Labs , using a crystal of silicon carbide and a cat's-whisker detector . Russian inventor Oleg Losev reported the 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, partly due to

1462-574: A phosphor-silicon mixture on the LED using techniques such as jet dispensing, and 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. Some "remote phosphor" LED light bulbs use a single plastic cover with YAG phosphor for one or several blue LEDs, instead of using phosphor coatings on single-chip white LEDs. Ce:YAG phosphors and epoxy in LEDs can degrade with use, and

1548-508: A red light-emitting diode. GaAsP was the basis for the first wave of commercial LEDs emitting visible light. It was mass produced by the Monsanto and Hewlett-Packard companies and used widely for displays in calculators and wrist watches. M. George Craford , a former graduate 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 designed

1634-485: A slightly more truncated red vision. Most other vertebrates (birds, lizards, fish, etc.) have retained their tetrachromacy , including UVS opsins that extend further into the ultraviolet than humans' VS opsin. The sensitivity of avian UVS opsins vary greatly, from 355–425 nm, and LWS opsins from 560–570 nm. This translates to some birds with a visible spectrum on par with humans, and other birds with greatly expanded sensitivity to UV light. The LWS opsin of birds

1720-484: 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. Although tetrachromatic white LEDs have excellent color rendering capability, they often have poor luminous efficacy. Trichromatic white LEDs are in between, having both good luminous efficacy (>70 lm/W) and fair color rendering capability. Visible spectrum The visible spectrum

1806-430: Is reflected and some of the beam passes into and through the glass, emerging as different-colored bands. Newton hypothesized light to be made up of "corpuscles" (particles) of different colors, with the different colors of light moving at different speeds in transparent matter, red light moving more quickly than violet in glass. The result is that red light is bent ( refracted ) less sharply than violet as it passes through

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1892-416: Is a semiconductor device that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes , releasing energy in the form of photons . The color of the light (corresponding to the energy of the photons) is determined by the energy required for electrons to cross the band gap of the semiconductor. White light is obtained by using multiple semiconductors or

1978-404: Is absorbed by the ocular media (lens and cornea), it may fluoresce and be released at a lower energy (longer wavelength) that can then be absorbed by the opsins. For example, when the lens absorbs 350 nm light, the fluorescence emission spectrum is centered on 440 nm. In addition to the photopic and scotopic systems, humans have other systems for detecting light that do not contribute to

2064-495: Is at about 590 nm. Mantis shrimp exhibit up to 14 opsins, enabling a visible range of less than 300 nm to above 700 nm. Some snakes can "see" radiant heat at wavelengths between 5 and 30  μm to a degree of accuracy such that a blind rattlesnake can target vulnerable body parts of the prey at which it strikes, and other snakes with the organ may detect warm bodies from a meter away. It may also be used in thermoregulation and predator detection. Spectroscopy

2150-550: Is difficult but desirable since it takes advantage of existing semiconductor manufacturing infrastructure. It allows for the wafer-level packaging of LED dies resulting in extremely small LED packages. GaN is often deposited using metalorganic vapour-phase epitaxy (MOCVD), and it also uses lift-off . Even though white light can be created using individual red, green and blue LEDs, this results in poor color rendering , since only three narrow bands of wavelengths of light are being emitted. The attainment of high efficiency blue LEDs

2236-492: Is difficult on silicon , while others, like the University of Cambridge, choose a multi-layer structure, in order to reduce (crystal) lattice mismatch and different thermal expansion ratios, to avoid cracking of the LED chip at high temperatures (e.g. during manufacturing), reduce heat generation and increase luminous efficiency. Sapphire substrate patterning can be carried out with nanoimprint lithography . GaN-on-Si

2322-490: Is mediated by rod cells . Each of these functions have different visible ranges. However, discussion on the visible range generally assumes photopic vision. The visible range of most animals evolved to match the optical window , which is the range of light that can pass through the atmosphere. The ozone layer absorbs almost all UV light (below 315 nm). However, this only affects cosmic light (e.g. sunlight ), not terrestrial light (e.g. Bioluminescence ). Before reaching

2408-794: Is more apparent with higher concentrations of Ce:YAG in phosphor-silicone mixtures, because the Ce:YAG decomposes with use. The output of LEDs can shift to yellow over time due to degradation of the silicone. There are several variants of Ce:YAG, and manufacturers in many cases do not reveal the exact composition of their Ce:YAG offerings. Several other phosphors are available for phosphor-converted LEDs to produce several colors such as red, which uses nitrosilicate phosphors, and many other kinds of phosphor materials exist for LEDs such as phosphors based on oxides, oxynitrides, oxyhalides, halides, nitrides, sulfides, quantum dots, and inorganic-organic hybrid semiconductors. A single LED can have several phosphors at

2494-599: Is perceived as white light, with improved color rendering compared to wavelengths from the blue LED/YAG phosphor combination. The first white LEDs were expensive and inefficient. The light output then increased exponentially . The latest research and development has been propagated by Japanese manufacturers such as Panasonic and Nichia , and by Korean and Chinese manufacturers such as Samsung , Solstice, Kingsun, Hoyol and others. This trend in increased output has been called Haitz's law after Roland Haitz. Light output and efficiency of blue and near-ultraviolet LEDs rose and

2580-716: Is sometimes reported to have a peak wavelength above 600 nm, but this is an effective peak wavelength that incorporates the filter of avian oil droplets . The peak wavelength of the LWS opsin alone is the better predictor of the long-wave limit. A possible benefit of avian UV vision involves sex-dependent markings on their plumage that are visible only in the ultraviolet range. Teleosts (bony fish) are generally tetrachromatic. The sensitivity of fish UVS opsins vary from 347-383 nm, and LWS opsins from 500-570 nm. However, some fish that use alternative chromophores can extend their LWS opsin sensitivity to 625 nm. The popular belief that

2666-601: Is the band of the electromagnetic spectrum that is visible to the human eye . Electromagnetic radiation in this range of wavelengths is called visible light (or simply light). The optical spectrum is sometimes considered to be the same as the visible spectrum, but some authors define the term more broadly, to include the ultraviolet and infrared parts of the electromagnetic spectrum as well, known collectively as optical radiation . A typical human eye will respond to wavelengths from about 380 to about 750 nanometers . In terms of frequency, this corresponds to

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2752-419: Is the study of objects based on the spectrum of color they emit, absorb or reflect. Visible-light spectroscopy is an important tool in astronomy (as is spectroscopy at other wavelengths), where scientists use it to analyze the properties of distant objects. Chemical elements and small molecules can be detected in astronomical objects by observing emission lines and absorption lines . For example, helium

2838-451: 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, similar to a fluorescent lamp . The yellow phosphor is cerium -doped YAG crystals suspended in the package or coated on the LED. This YAG phosphor causes white LEDs to appear yellow when off, and

2924-934: The Nobel Prize in Physics in 2014 for "the invention of efficient blue light-emitting diodes, which has enabled bright and energy-saving white light sources." 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 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

3010-553: The U.S. patent office issued the two inventors the patent for the GaAs infrared 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 an 890 nm light output. In October 1963, TI announced

3096-457: The human eye as a pure ( saturated ) color. Also unlike most lasers, its radiation is not spatially coherent , so it cannot approach the very high intensity characteristic of lasers . By selection of different semiconductor materials , single-color LEDs can be made that emit light in a narrow band of wavelengths from near-infrared through the visible spectrum and into the ultraviolet range. The required operating voltages of LEDs increase as

3182-440: The lens . Insensitivity to IR light is limited by the spectral sensitivity functions of the visual opsins. The range is defined psychometrically by the luminous efficiency function , which accounts for all of these factors. In humans, there is a separate function for each of two visual systems, one for photopic vision , used in daylight, which is mediated by cone cells , and one for scotopic vision , used in dim light, which

3268-404: The retina , light must first transmit through the cornea and lens . UVB light (< 315 nm) is filtered mostly by the cornea, and UVA light (315–400 nm) is filtered mostly by the lens. The lens also yellows with age, attenuating transmission most strongly at the blue part of the spectrum. This can cause xanthopsia as well as a slight truncation of the short-wave (blue) limit of

3354-427: The 17th century, Isaac Newton discovered that prisms could disassemble and reassemble white light, and described the phenomenon in his book Opticks . He was the first to use the word spectrum ( Latin for "appearance" or "apparition") in this sense in print in 1671 in describing his experiments in optics . Newton observed that, when a narrow beam of sunlight strikes the face of a glass prism at an angle, some

3440-451: The 3-subpixel model for digital displays. The technology uses a gallium nitride semiconductor that emits light of different frequencies modulated by voltage changes. A prototype display achieved a resolution of 6,800 PPI or 3k x 1.5k pixels. In a light-emitting diode, the recombination of electrons and electron holes in a semiconductor produces light (be it infrared, visible or UV), a process called " electroluminescence ". The wavelength of

3526-472: The L-opsin, there are also reports that pulsed NIR lasers can evoke green, which suggests two-photon absorption may be enabling extended NIR sensitivity. Similarly, young subjects may perceive ultraviolet wavelengths down to about 310–313 nm, but detection of light below 380 nm may be due to fluorescence of the ocular media, rather than direct absorption of UV light by the opsins. As UVA light

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3612-839: The Luxeon C in 2015, a family of high-power LED light sources capable of delivering multiple colors from a single focal length. Lumileds LEDs are used in the Bridge of Peace , an illuminated pedestrian bridge in Tbilisi , and in the Times Square Ball made by Waterford Crystal . Lumileds had a history of patent disputes with competitor Epistar over the use of AlInGaP LED technology. However, in September, 2009, Philips Lumileds signed an agreement to license AlInGaP technology to Epistar. LEDs A light-emitting diode ( LED )

3698-637: The US high-tech sector. The deal was cancelled in January, 2016, due to the CFIUS concerns. CFIUS concerns were based on transfer of gallium nitride semiconductor technology, which is used in LEDs as well as defense applications. In December 2016, Philips announced that it has signed an agreement to sell an 80.1% interest in Lumileds to certain funds managed by affiliates of Apollo Global Management . Philips retains

3784-538: The area around the Sun which appears white because the light is not scattered as much). The optical window is also referred to as the "visible window" because it overlaps the human visible response spectrum. The near infrared (NIR) window lies just out of the human vision, as well as the medium wavelength infrared (MWIR) window, and the long-wavelength or far-infrared (LWIR or FIR) window, although other animals may perceive them. Colors that can be produced by visible light of

3870-800: The blending of the colors. Since LEDs have slightly different emission patterns, the color balance may change depending on the angle of view, even if the RGB sources are in a single package, so RGB diodes are seldom used to produce white lighting. Nonetheless, this method has many applications because of the flexibility of 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

3956-1088: 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 unalloyed 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 AlGaN and AlGaInN , even shorter wavelengths are achievable. Near-UV emitters at wavelengths around 360–395 nm are already cheap and often encountered, for example, as black light lamp replacements for inspection of anti- counterfeiting UV watermarks in documents and bank notes, and for UV curing . Substantially more expensive, shorter-wavelength diodes are commercially available for wavelengths down to 240 nm. As

4042-614: The common goldfish is the only animal that can see both infrared and ultraviolet light is incorrect, because goldfish cannot see infrared light. The visual systems of invertebrates deviate greatly from vertebrates, so direct comparisons are difficult. However, UV sensitivity has been reported in most insect species. Bees and many other insects can detect ultraviolet light, which helps them find nectar in flowers. Plant species that depend on insect pollination may owe reproductive success to their appearance in ultraviolet light rather than how colorful they appear to humans. Bees' long-wave limit

4128-417: 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 were demonstrated in 2014 to produce 303 lumens per watt of electricity (lm/W); some can last up to 100,000 hours. Commercially available LEDs have an efficiency of up to 223 lm/W as of 2018. A previous record of 135 lm/W

4214-458: The days of the week. The human eye is relatively insensitive to indigo's frequencies, and some people who have otherwise-good vision cannot distinguish indigo from blue and violet. For this reason, some later commentators, including Isaac Asimov , have suggested that indigo should not be regarded as a color in its own right but merely as a shade of blue or violet. Evidence indicates that what Newton meant by "indigo" and "blue" does not correspond to

4300-460: The definition of the limits is not standard and will change depending on the industry. For example, some industries may be concerned with practical limits, so would conservatively report 420–680 nm, while others may be concerned with psychometrics and achieving the broadest spectrum would liberally report 380–750, or even 380–800 nm. The luminous efficiency function in the NIR does not have

4386-434: The early 19th century, the concept of the visible spectrum became more definite, as light outside the visible range was discovered and characterized by William Herschel ( infrared ) and Johann Wilhelm Ritter ( ultraviolet ), Thomas Young , Thomas Johann Seebeck , and others. Young was the first to measure the wavelengths of different colors of light, in 1802. The connection between the visible spectrum and color vision

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4472-543: The emitted wavelengths become shorter (higher energy, red to blue), because of their increasing semiconductor band gap. Blue LEDs 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 nitride (AlGaN) of varying Al/Ga fraction can be used to manufacture

4558-496: The field of luminescence with research on radium . Hungarian Zoltán Bay together with György Szigeti patenting a lighting device in Hungary in 1939 based on silicon carbide, with an option on boron carbide, that emitted white, yellowish white, or greenish white depending on impurities present. Kurt Lehovec , Carl Accardo, and Edward Jamgochian explained these first LEDs in 1951 using an apparatus employing SiC crystals with

4644-612: The first commercial hemispherical LED, the SNX-110. In the 1960s, several laboratories focused on LEDs that would emit visible light. A particularly important device was demonstrated by Nick Holonyak on October 9, 1962, while he was working for General Electric in Syracuse, New York . The device used the semiconducting alloy gallium phosphide arsenide (GaAsP). It was the first semiconductor laser to emit visible light, albeit at low temperatures. At room temperature it still functioned as

4730-521: The first commercially available blue LED, based on 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

4816-721: The first high-brightness, high-efficiency LEDs for optical fiber telecommunications by inventing new semiconductor materials specifically adapted to optical fiber transmission wavelengths. Until 1968, visible and infrared LEDs were extremely costly, on the order of US$ 200 per unit, and so had little practical use. The first commercial visible-wavelength LEDs used GaAsP semiconductors and 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 calculators, TVs, radios, telephones, as well as watches. The Hewlett-Packard company (HP)

4902-407: The important GaN deposition on sapphire substrates and the demonstration of p-type doping of GaN. This new development revolutionized LED lighting, making high-power blue light sources practical, leading to the development of technologies like Blu-ray . Nakamura was awarded the 2006 Millennium Technology Prize for his invention. Nakamura, Hiroshi Amano , and Isamu Akasaki were awarded

4988-475: The lens, mice have a UVS opsin that can detect down to 340 nm. While allowing UV light to reach the retina can lead to retinal damage, the short lifespan of mice compared with other mammals may minimize this disadvantage relative to the advantage of UV vision. Dogs have two cone opsins at 429 nm and 555 nm, so see almost the entire visible spectrum of humans, despite being dichromatic. Horses have two cone opsins at 428 nm and 539 nm, yielding

5074-417: The light depends on the energy band gap of the semiconductors used. Since these materials have a high index of refraction, design features of the devices such as special optical coatings and die shape are required to efficiently emit light. Unlike a laser , the light emitted from an LED is neither spectrally coherent nor even highly monochromatic . Its spectrum is sufficiently narrow that it appears to

5160-420: The light produced is engineered to suit the human eye. Because of metamerism , it is possible to have quite different spectra that appear white. 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. An orange or cyan object could appear with the wrong color and much darker as the LED or phosphor does not emit

5246-416: The modern meanings of those color words. Comparing Newton's observation of prismatic colors with a color image of the visible light spectrum shows that "indigo" corresponds to what is today called blue, whereas his "blue" corresponds to cyan . In the 18th century, Johann Wolfgang von Goethe wrote about optical spectra in his Theory of Colours . Goethe used the word spectrum ( Spektrum ) to designate

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5332-458: The peak wavelengths of opsins with those of typical humans (S-opsin at 420 nm and L-opsin at 560 nm). Most mammals have retained only two opsin classes (LWS and VS), due likely to the nocturnal bottleneck . However, old world primates (including humans) have since evolved two versions in the LWS class to regain trichromacy. Unlike most mammals, rodents' UVS opsins have remained at shorter wavelengths. Along with their lack of UV filters in

5418-448: The phosphors, the Ce:YAG phosphor converts blue light to green and red (yellow) light, and the PFS phosphor converts blue light to red light. The color, emission spectrum or color temperature of white phosphor converted and other phosphor converted LEDs can be controlled by changing the concentration of several phosphors that form a phosphor blend used in an LED package. The 'whiteness' of

5504-599: 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 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). There are two primary ways of producing white light-emitting diodes. One

5590-405: The position of the individual opsin spectral sensitivity functions therefore affects the luminous efficiency function and the visible range. For example, the long-wave (red) limit changes proportionally to the position of the L-opsin. The positions are defined by the peak wavelength (wavelength of highest sensitivity), so as the L-opsin peak wavelength blue shifts by 10 nm, the long-wave limit of

5676-459: The primary visual system . For example, melanopsin has an absorption range of 420–540 nm and regulates circadian rhythm and other reflexive processes. Since the melanopsin system does not form images, it is not strictly considered vision and does not contribute to the visible range. The visible spectrum is defined as that visible to humans, but the variance between species is large. Not only can cone opsins be spectrally shifted to alter

5762-479: The prism, creating a spectrum of colors. Newton originally divided the spectrum into six named colors: red , orange , yellow , green , blue , and violet . He later added indigo as the seventh color since he believed that seven was a perfect number as derived from the ancient Greek sophists , of there being a connection between the colors, the musical notes, the known objects in the Solar System , and

5848-468: The remaining 19.9% interest in Lumileds. The transaction was completed in July 2017, under customary closing conditions, including the relevant regulatory approvals. IP strategist Keaton Parekh helped separate the intellectual property portfolio after the spin off from Philips. On August 29, 2022, Lumileds filed for Chapter 11 bankruptcy protection. The company reached an agreement to enter restructuring in

5934-421: 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 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

6020-480: The same time. Some LEDs use phosphors made of glass-ceramic or composite phosphor/glass materials. Alternatively, the LED chips themselves can be coated with a thin coating of phosphor-containing material, called a conformal coating. The temperature of the phosphor during operation and how it is applied limits the size of an LED die. Wafer-level packaged white LEDs allow for extremely small LEDs. In 2024, QPixel introduced as polychromatic LED that could replace

6106-408: The space between the crystals allow some blue light to pass through in LEDs with partial phosphor conversion. Alternatively, white LEDs may use other phosphors like manganese(IV)-doped potassium fluorosilicate (PFS) or other engineered phosphors. PFS assists in red light generation, and is used in conjunction with conventional Ce:YAG phosphor. In LEDs with PFS phosphor, some blue light passes through

6192-547: 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 ). 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

6278-480: 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 for epitaxy , which

6364-569: The team at Fairchild led by optoelectronics pioneer Thomas Brandt to achieve the needed cost reductions. LED producers have continued to use these methods as of about 2009. The early red LEDs were bright enough 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, other colors became widely available and appeared in appliances and equipment. Early LEDs were packaged in metal cases similar to those of transistors, with

6450-461: The very inefficient light-producing properties of silicon carbide, the semiconductor Losev used. In 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

6536-405: The visible range, but vertebrates with 4 cones (tetrachromatic) or 2 cones (dichromatic) relative to humans' 3 (trichromatic) will also tend to have a wider or narrower visible spectrum than humans, respectively. Vertebrates tend to have 1-4 different opsin classes: Testing the visual systems of animals behaviorally is difficult, so the visible range of animals is usually estimated by comparing

6622-532: The visible spectrum also shifts 10 nm. Large deviations of the L-opsin peak wavelength lead to a form of color blindness called protanomaly and a missing L-opsin ( protanopia ) shortens the visible spectrum by about 30 nm at the long-wave limit. Forms of color blindness affecting the M-opsin and S-opsin do not significantly affect the luminous efficiency function nor the limits of the visible spectrum. Regardless of actual physical and biological variance,

6708-433: The visible spectrum. Subjects with aphakia are missing a lens, so UVA light can reach the retina and excite the visual opsins; this expands the visible range and may also lead to cyanopsia . Each opsin has a spectral sensitivity function, which defines how likely it is to absorb a photon of each wavelength. The luminous efficiency function is approximately the superposition of the contributing visual opsins . Variance in

6794-538: The wavelength it reflects. The best color rendition LEDs use a mix of phosphors, resulting in less efficiency and better color rendering. The first white light-emitting diodes (LEDs) were offered for sale in the autumn of 1996. Nichia made some of the first white LEDs which were based on blue LEDs with Ce:YAG phosphor. Ce:YAG is often grown using the Czochralski method . Mixing red, green, and blue sources to produce white light needs electronic circuits to control

6880-618: Was achieved by Nichia in 2010. Compared to incandescent bulbs, this is a huge increase in electrical efficiency, and even though LEDs are more expensive to purchase, overall lifetime cost is significantly cheaper than that of incandescent bulbs. The LED chip is encapsulated inside a small, plastic, white mold although sometimes an LED package can incorporate a reflector. It can be encapsulated using resin ( polyurethane -based), silicone, or epoxy containing (powdered) Cerium-doped YAG phosphor particles. The viscosity of phosphor-silicon mixtures must be carefully controlled. After application of

6966-415: Was engaged in research and development (R&D) on practical LEDs between 1962 and 1968, by a research team under Howard C. Borden, Gerald P. Pighini at HP Associates and HP Labs . During this time HP collaborated with Monsanto Company on developing the first usable LED products. The first usable LED products were HP's LED display and Monsanto's LED indicator lamp , both launched in 1968. Monsanto

7052-414: Was explored by Thomas Young and Hermann von Helmholtz in the early 19th century. Their theory of color vision correctly proposed that the eye uses three distinct receptors to perceive color. The visible spectrum is limited to wavelengths that can both reach the retina and trigger visual phototransduction (excite a visual opsin ). Insensitivity to UV light is generally limited by transmission through

7138-433: 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 the first blue electroluminescence from zinc-doped gallium nitride, though

7224-443: Was quickly followed by the development of the first white LED . In this device a Y 3 Al 5 O 12 :Ce (known as " YAG " or Ce:YAG phosphor) cerium -doped phosphor coating produces yellow light through fluorescence . The combination of that yellow with remaining blue light appears white to the eye. Using different phosphors produces green and red light through fluorescence. The resulting mixture of red, green and blue

7310-571: Was the first intelligent LED display, and was a revolution in digital display technology, replacing the Nixie tube and becoming the basis for later LED displays. 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 (developed by Jean Hoerni , ). The combination of planar processing for chip fabrication and innovative packaging methods enabled

7396-484: Was the first organization to mass-produce visible LEDs, using Gallium arsenide phosphide (GaAsP) in 1968 to produce red LEDs suitable for indicators. Monsanto had previously offered to supply HP with GaAsP, but HP decided to grow its own GaAsP. In February 1969, Hewlett-Packard introduced the HP Model 5082-7000 Numeric Indicator, the first LED device to use integrated circuit (integrated LED circuit ) technology. It

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