Osram Opto develops projection LED for smartphones and cameras

June 04, 2012 // By Christoph Hammerschmidt
The next cool feature for smartphones and cameras could be an integrated miniature projector that displays images on a much larger surface than existing displays. The greatest challenge so far for embedded LED projection technology is the limited efficiency of the green light emitting diodes. This is because high brightness is essential if the projected image will be seen with ambient light. Osram Opto Semiconductors has developed something that could resolve the problem.

Efficient LEDs for red and blue light have been available for some time but LEDs that produce green with acceptable output have been rare. The new Osram Ostar Projection Cube has now plugged this important gap, the company claims. At 110 lumen per watt (lm/W) it is more efficient than other previously available green LEDs in the embedded projection sector. For the first time, the Osram Ostar Projection Cube enables high output to be achieved in embedded projectors. “The new LED almost doubles the brightness in smartphone applications. Thus embedded projectors with a system brightness of up to 25 lumen are possible“, said Wolfgang Schnabel, Marketing Manager Projection at Osram Opto Semiconductors. This means that the image is clearly visible even at ambient light and, thanks to the efficiency of LED technology the projector can also be used in mobile applications with limited battery capacity.

The green LED is available in two versions – with a 1 mm edge length chip and with a 0.75 mm edge length. The Osram Ostar Projection Cube is therefore suitable for all standard imager formats in mobile terminals. The two LED versions are also very bright. Depending on the size of the chip, they produce 260 lm at 700 mA and 2.3 W or 130 lm at 350 mA and 1.2 W. This high luminance from a small surface area is made possible with the aid of special encapsulation. This sharply defines the light surface so the light is emitted from this defined surface without package reflections. With an area of 3.8 x 4.1 mm² and a height of only 0.6 mm the new LED enables extremely low-profile projection units to be designed – ideal for modern smartphone and camera designs.

The Projection Cube does not have a glass cover, which means that external optics can be placed very close to it and the light can be used efficiently. Francis Nguyen from Osram Opto