A novel projection cube LED for smartphones and cameras
One of the greatest challenges, so far for lighting technology, has been the limited efficiency of green LEDs. High brightness is essential if a projected image is to be seen with ambient light.
Now, Osram Opto Semiconductors has released the Ostar Projection LED Cube. The integrated miniature projector, which uses LEDs as the light source, can display images on a much larger surface than existing displays for smartphones and cameras.
The new Osram Ostar Projection Cube LED for "embedded projection" for brilliant projected colours from a smartphone
Efficient LEDs for red and blue light have been available for some time now but LEDs that produce green with acceptable output have been rare. Osram new says its Ostar Projection Cube has now plugged this important gap. At 110 lumen per watt (lm/W) it is claimed to be much more efficient than all other previously available green LEDs in the embedded projection sector.
The Ostar Projection Cube enables high output to be achieved in embedded projectors. "The new LED almost doubles the brightness in smartphone applications so embedded projectors with a system brightness of up to 25 lumen are possible", says Wolfgang Schnabel, Marketing Manager Projection at Osram Opto Semiconductors.
This means that the image is clearly visible even with ambient light and, thanks to the efficiency of LED technology, the projector can also be used in mobile applications with limited battery capacity.
The new green LED chip comes in two sizes; 1 x 1 mm and 0.75 x 0.75 mm. The Osram Ostar Projection Cube is therefore suitable for most 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 mm²and a height of 0.6 mm the new LED enables extremely low-profile projection units to be designed, which is ideal for modern smartphone and camera designs. The Osram Ostar 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.
With a thermal resistance of typically 6 K/W, the power draw is 2.3 W for the 1 mm2 chip and 1.2 W for the 0.75 x 0.75 mm chip. Osram says the LED has a lifetime of over 20,000 hours.
Francis Nguyen from Osram Opto Semiconductors will present this new LED at the Projection Summit 2012 in Las Vegas during his talk on the "Evolution of LEDs used in Picoprojectors" on June 11th, 2012.
