LED Type Development
The earliest use of semiconductor n junction light-emitting Principle made of LED light source was published in the early 1960s. The material used at that time was gaasp, Aglow (λp=650nm), when the driving current is 20 ma, the luminous flux is only a few lumens, the corresponding luminous efficiency of about 0.1 lumens/watts.
In the mid 70, the introduction of elements in and N, led to the production of green light (λp=555nm), yellow (λp=590nm) and orange Light (λp=610nm), light efficiency also increased to 1 lumens/watts.
By the early 80, there was a gaalas led light source that led to a red light effect of up to 10 lumens/watts.
The early 90, red, yellow gaalinp and green, Blue Gainn Two of new materials developed successfully, LED light efficiency has been greatly improved. In 2000, the former led in the Red and orange area (λp=615nm) of light efficiency reached 100 lumens/watts, while the latter made of led in the green area (λp=530nm) light efficiency can reach 50 lumens/watts.
Monochrome LED applications: The original LED used as the indicator light source for instrumentation, and later a variety of light color led in traffic lights and large-scale display of the wide application, resulting in good economic and social benefits. In the case of a 12-inch red traffic signal, in the United States, a long life, low light efficiency of 140-watt incandescent lamps as a light source, it produces 2000 lumens of white light. After the red filter, the light loses 90%, leaving only 200 lumens of red. In the new design of the lamp, lumileds company used 18 red LED light source, including circuit losses, a total power consumption of 14 watts, you can produce the same light effect.
The automobile lamp is also an important field of LED light source application. In 1987, our country began to install high brake lights on the car, because of the fast response speed (nanosecond), you can let the driver of the trailing vehicle know the driving condition, reduce the car rear-end accident occurred.
In addition, LED lights in the outdoor red, green, blue full-color display, key button micro-flashlight and other fields have been applied.