Enormous increase in brightness for green

The prototype of a green LED based on the OSTAR platform from OSRAM Opto Semiconductors is twice as bright as its predecessors and has a luminous surface that is perfectly uniform. This single-chip LED benefits from the latest chip technology and a green phosphor converter. Initial samples are already available, and the process of finding partners to develop appropriate LED office projectors is already under way. The semiconductor specialist expects the LED to be launched on the market in the summer of 2011.

Now that RGB LED have already conquered the market for pico projectors the next segment in their sights is that of office projectors. This has been made possible by the enormous brightness increase of green LEDs. The prototype with a single chip achieves 410 lm and emits at a wavelength of 553 nm. Since a greater proportion of green than red or blue is needed in a projector to produce white light, the increase in the brightness of the green LED has a significant effect on the overall system brightness. With these LED prototypes it is possible to produce systems that provide the system brightness of 2000 lm that is needed for office projectors. LED projectors will therefore be powerful enough for large diagonals of more than two meters. Such applications have only been possible with projectors that use conventional light sources such as high-intensity discharge lamps.

“Doubling the brightness of the green LED is a giant leap forward and removes the restriction that LEDs are suitable only for small projectors”, said Volker Mertens, Director Marketing Industry at OSRAM Opto Semiconductors. Apart from providing brilliant image reproduction with saturated colors, LEDs enable projectors to be virtually maintenance-free because they have a life of 30,000 hours. By contrast, high-intensity discharge lamps need to be replaced after only about 4000 hours. Projectors with LEDs also respond more quickly to on/off switching, and they support stepless dimming. They can therefore adapt very easily to ambient light conditions and reduce energy consumption. The color space can be set with a high degree of flexibility thanks to electronic control of the individual colors.

Thanks to new high-brightness green LEDs, the LED projectors of the future will be able to produce images with diagonals of several meters. The projected images themselves will appear brighter for the same lumen value than those produced by conventional light sources thanks to the saturated colors of the LEDs used.