30-08-2017, 10:47 AM
A light emitting diode (LED) is a two conductor semiconductor light source. It is a p-n junction diode that emits light when it is activated. When a suitable voltage is applied to the conductors, the electrons are able to recombine with the electron holes inside the device, releasing energy in the form of photons. This effect is called electroluminescence, and the color of light (corresponding to photon energy) is determined by the semiconductor energy bandwidth. The LEDs are typically small (less than 1 mm2) and integrated optical components can be used to form the radiation pattern.
Appearing as practical electronic components in 1962, the first LEDs emitted infrared light of low intensity. Infrared LEDs are often used as transmitter elements in remote control circuits, such as those found on remote controls for a wide variety of consumer electronics. The first visible light LEDs were also low intensity and limited to red. Modern LEDs are available through visible, ultraviolet and infrared wavelengths, with a very high brightness.
Early LEDs were often used as indicator lamps for electronic devices, replacing small incandescent light bulbs. They were soon packaged in numerical readings in the form of seven-segment displays and were commonly seen on digital clocks. Recent developments have produced LEDs suitable for ambient and task lighting. LEDs have led to new displays and sensors, while their high switching speeds are useful in advanced communications technology.
LEDs have many advantages over incandescent light sources, including lower power consumption, longer life, improved physical robustness, smaller size and faster switching. Light emitting diodes are used in applications as diverse as aviation lighting, automotive headlights, advertising, general lighting, traffic signs, camera flashes and illuminated backlit. As of 2017, the LED lights of the house lighting are as cheap or cheaper than the sources of comparable compact fluorescent lamps. They are also much more energy efficient and undoubtedly have fewer environmental concerns related to their disposal.
Unlike a laser, the colour of light emitted by an LED is neither coherent nor monochromatic, but the spectrum is narrow with respect to human vision, and for most purposes the light of a single diode element can considered monochromatic.
Appearing as practical electronic components in 1962, the first LEDs emitted infrared light of low intensity. Infrared LEDs are often used as transmitter elements in remote control circuits, such as those found on remote controls for a wide variety of consumer electronics. The first visible light LEDs were also low intensity and limited to red. Modern LEDs are available through visible, ultraviolet and infrared wavelengths, with a very high brightness.
Early LEDs were often used as indicator lamps for electronic devices, replacing small incandescent light bulbs. They were soon packaged in numerical readings in the form of seven-segment displays and were commonly seen on digital clocks. Recent developments have produced LEDs suitable for ambient and task lighting. LEDs have led to new displays and sensors, while their high switching speeds are useful in advanced communications technology.
LEDs have many advantages over incandescent light sources, including lower power consumption, longer life, improved physical robustness, smaller size and faster switching. Light emitting diodes are used in applications as diverse as aviation lighting, automotive headlights, advertising, general lighting, traffic signs, camera flashes and illuminated backlit. As of 2017, the LED lights of the house lighting are as cheap or cheaper than the sources of comparable compact fluorescent lamps. They are also much more energy efficient and undoubtedly have fewer environmental concerns related to their disposal.
Unlike a laser, the colour of light emitted by an LED is neither coherent nor monochromatic, but the spectrum is narrow with respect to human vision, and for most purposes the light of a single diode element can considered monochromatic.