The Evolution of LED Lights

The first commercial LEDs were commonly used as replacements for incandescent indicators, first in expensive equipment such as laboratory and electronics test equipment, then later in such appliances as TVs, radios, telephones, calculators, and even watches. These red LEDs were bright enough only for use as indicators, as the light output was not enough to illuminate an area. Later, other colors became widely available and also appeared in appliances and equipment.

As the LED materials technology became more advanced, the light output was increased, while maintaining the efficiency and the reliability to an acceptable level. With the development of high efficiency and high power LEDs it has become possible to incorporate LEDs in lighting and illumination. Replacement light bulbs have been made as well as dedicated fixtures and LED lamps. LEDs are used as street lights and in other architectural lighting where color changing is used.

The mechanical robustness and long lifetime is used in automotive lighting on cars, motorcycles and on bicycle lights. LEDs are also suitable for backlighting for LCD televisions and lightweight laptop displays and light source for DLP projectors. RGB LEDs increase the color gamut by as much as 45%. Screen for TV and computer displays can be made increasingly thin using LEDs for backlighting. The lack of IR/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.

Since LEDs are small, durable and require little power they are used in hand held devices such as flashlights. LED strobe lights or camera flashes operate at a safe, low voltage, as opposed to the 250+ volts commonly found in xenon flash lamp-based lighting. This is particularly applicable to cameras on mobile phones, where space is at a premium and bulky voltage-increasing circuitry is undesirable. LEDs are used for infrared illumination in night vision applications including security cameras. A ring of LEDs around a video camera, aimed forward into a retro reflective background, allows chroma keying in video productions.

Chroma key is a technique for mixing two images or frames together, in which a color from one image is removed (or made transparent), revealing another image behind it. This technique is also referred to as color keying, color-separation overlay, green screen, and blue screen. It is commonly used for weather forecast broadcasts, wherein the presenter appears to be standing in front of a large map, but in the studio it is actually a large blue or green background. The meteorologist stands in front of a blue screen, and then different weather maps are added on those parts in the image where the color is blue. If the meteorologist himself wears blue clothes, his clothes will become replaced with the background video. This also works for green screens, since blue and green are considered the colors least like skin tone. This technique is also used in the entertainment industry.

LEDs are used for decorative lighting as well. Decorative LED lighting is used for indoor/outdoor decor, limousines, cargo trailers, cruise ships, RVs, boats, automobiles, and utility trucks. Decorative LED lighting can also come in the form of Lited Logo Panels and Engravings and Step and Aisle lighting in theaters and auditoriums.

Source: Wikipedia