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The wavelength of the light emitted is a function of the band gap of the semiconductor material used; materials such as gallium arsenide, and others, with various trace doping elements, are used to produce different colors of light. Another type of LED uses a quantum dot which can have its properties and wavelength adjusted by its size. Light ...
In recent years light-emitting diodes (LEDs) are becoming increasingly efficient leading to an extraordinary increase in the use of solid state lighting. In many situations, controlling the light emission of LEDs may be done most effectively by using the principles of nonimaging optics. [51]
EISA 2007 is an effort to increase lighting efficiency by 25-30%. Opposition to EISA 2007 is demonstrated by the Better Use of Light Bulbs Act and the Light Bulb Freedom of Choice Act. The efforts to increase lighting efficiency are also demonstrated by the Energy Star program and the increase efficiency goals by 2011 and 2013.
Optical computer mice use LEDs as a light source for the miniature camera within the mouse. LEDs are useful for machine vision because they provide a compact, reliable source of light. LED lamps can be turned on and off to suit the needs of the vision system, and the shape of the beam produced can be tailored to match the system's requirements.
The reflection is most commonly reduced by using a dome-shaped (half-sphere) package with the diode in the center so that the outgoing light rays strike the surface perpendicularly, at which angle the reflection is minimized. Substrates that are transparent to the emitted wavelength, and backed by a reflective layer, increase the LED efficiency.
A 230-volt LED filament lamp, with an E27 base. The filaments are visible as the eight yellow vertical lines. An assortment of LED lamps commercially available in 2010: floodlight fixtures (left), reading light (center), household lamps (center right and bottom), and low-power accent light (right) applications An 80W Chips on board (COB) LED module from an industrial light luminaire, thermally ...
LED display of a TI-30 scientific calculator (c. 1978), which uses plastic lenses to increase the visible digit size X-Ray of a 1970s 8-digit LED calculator display. Until 1968, visible and infrared LEDs were extremely costly, on the order of US$200 per unit, and so had little practical use. [23]
Heat lamps may have a red coating to reduce the visible light emitted. Solid-state light emitting diodes can be produced to be efficient sources of near-monochromatic infrared energy. Such sources can be rapidly modulated for communication systems and control signals. A light emitting diode can be closely coupled to an optical fiber, allowing ...