| 1907: Henry Joseph Round discovers the physical | | | | advertising benefit from the advantages of LED, |
| effect of electroluminescence. But as he is working on | | | | particularly by using colored LED-modules. |
| a new radio direction finding method for marine | | | | Basic principles of LED (Light Emitting Diodes) |
| vessels this discovery is initially forgotten. | | | | - LED consists of several layers of semiconducting |
| 1962: The first red luminescence diode, type GaAsP, is | | | | material |
| launched. 1971: LED in other colors are available: green, | | | | - When an LED is operated with DC voltage light is |
| orange, yellow. There are continual improvements in | | | | generated in the active layer |
| the output and effectiveness of all LEDs. | | | | - The generated light is radiated directly or by |
| 1993: Highly efficient InGaN diodes emitting in the blue | | | | reflections -In contrast to lamps, which emit a |
| and green spectrum are demonstrated. The conditions | | | | continuous spectrum, an LED emits light in a certain |
| for creating white light are met. | | | | color |
| 1995: The first LED with white light created by | | | | - The color of the light depends on the used material |
| luminescence conversion is launched. | | | | - Two systems of material (AllnGaP and InGaN) are |
| For more than 30 years, LED have been used in | | | | used in order to produce LED with a high luminance in |
| various industrial applications from switch cabinets to | | | | all colors from blue to red and also in white |
| measuring instruments, in consumer products such as | | | | (luminescence conversion). Therefore different |
| HiFi- equipment, telephones or personal computers, in | | | | voltages are necessary in order to operate the diode |
| traffic signal installations for road and railway or in | | | | in conducting direction. |
| indoor and outdoor automotive lighting. automotive | | | | The production of white light |
| lighting. | | | | To produce white light, the light of blue LEDs is passed |
| In the last few years the efficacy of colored LED | | | | through yellow phosphors. The composition of the |
| increased up to amazing 100 lm/W and more | | | | phosphor determines the light color. |
| depending on the color and driving conditions. A trend | | | | The Chip Level Coating (CLC) process developed and |
| which will proceed in the future. | | | | patented by OSRAM ensures a degree of |
| As today's white LED reach efficacies up to 40-100 lm | | | | homogenity in the light produced that other processes |
| W (efficiency depends on color temperature and color | | | | cannot achieve. By selecting appropriate white LEDs, it |
| rendering) - they are more and more used in general | | | | is possible to offer LED systems with the same light |
| lighting. In emergency lighting as well as decorative | | | | colors as fluorescent lamps (Warm White, Neutral |
| lighting, they are already established in implementation | | | | White and Daylight). |
| area. Today, also applications such as illuminated | | | | |