1907: Henry Joseph Round discovers the physical effect of electroluminescence. But as he is working on a new radio direction finding method for marine vessels this discovery is initially forgotten.
1962: The first red luminescence diode, type GaAsP, is launched.
1971: LED in other colors are available: green, orange, yellow. There are continual improvements in the output and effectiveness of all LEDs.
1993: Highly efficient InGaN diodes emitting in the blue and green spectrum are demonstrated. The conditions for creating white light are met.
1995: The first LED with white light created by luminescence conversion is launched.
For more than 30 years, LED have been used in various industrial applications from switch cabinets to measuring instruments, in consumer products such as HiFi- equipment, telephones or personal computers, in traffic signal installations for road and railway or in indoor and outdoor automotive lighting.
In the last few years the efficacy of colored LED increased up to amazing 100 lm/W and more depending on the color and driving conditions. A trend which will proceed in the future.
As today's white LED reach efficacies up to 40-100 lm/W (efficiency depends on color temperature and color rendering) - they are more and more used in general lighting. In emergency lighting as well as decorative lighting, they are already established in implementation area. Today, also applications such as illuminated advertising benefit from the advantages of LED, particularly by using colored LED-modules.
