September 19, 2006 Miniaturised projection systems have been spoken about for a long time, but with several viable technologies seemingly close to market, the day when you can carry a video projector at all times, just in case you need it is close. In February, we wrote about the matchbox-sized PVPro projector and now news from Faraunhoffer suggests that not-too-far down the track your handheld, digital camera, portable media player or phone might have a projector built-in. That’s the promise of a new technology for projectors that does not use conventional micro arrays, instead containing just a single mirror that can be rotated around two axes. Researchers at the Fraunhofer Institute for Photonic Microsystems IPMS in Dresden and the Fraunhofer Institute for Applied Optics and Precision Engineering IOF in Jena have developed an alternative to micro mirror arrays and the result is a projector the size of a sugar cube.
The challenge in miniaturisation the traditional projector is to overcome the physical limitations of the micro mirror array comprising millions of mirrors. These can be tilted in one plane and are evenly illuminated. By turning towards or away from the light source, they produce light or dark pixels that together form the projected image. But not only do the arrays preclude miniaturization, their prices also make it difficult for projectors to enter the consumer goods market.
“We use just one single mirror,” reveals Andreas Bräuer, director of the Microoptic Systems division at IOF. “This mirror can be tilted around two axes.”
The next obstacle in the miniaturization process is the light source. The customary high-pressure lamp will have to give way to small diode lasers if the projector is to shrink to the size of a sugar cube. While red and blue diode lasers are already small enough, green lasers are still too bulky. Today’s technology allows RGB projectors with a side length of ten by seven by three centimetres to be produced. Although this is still distinctly larger than a sugar cube, it is only a quarter the size of a standard projector. Researchers around the globe are attempting to scale down the green light source. Together with the blue and red diode lasers, it will ideally form the new red-green-blue source. “If green diode lasers are successfully reduced to the size of red ones, then RGB projectors the size of sugar cubes will become a reality,” states Bräuer.
Such would prove useful in many areas. The automotive industry, for example, requires small, cost-effective laser arrays to act as distance sensors that measure the gap between the car and the nearest object when parking. Sensors of this type are also used in robotics and installation technology. Yet another area of usage for the mini-lasers are digital projectors, which can be integrated in mobile devices such as laptops or PDAs.
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