BERLIN -- A projection display based on the mixing of red, green and blue laser beams was demonstrated for the first time at an exhibition here last week. Though the projection equipment is large and is still at a prototype stage, its use of a scanning laser beam is considered promising for systems that one day could enable very large-scale projections--up to 30 meters diagonally--for outdoor events and that could yield cool-running displays for home-theater applications.

The developer, Laser-Display-Technologie GmbH & Co KG (LDT, Heilbronn, Germany), also said it has taken delivery of silicon-based electrostatic micromirrors. The devices may be used to create small, reasonably priced scanners for inclusion in desktop equipment as an alternative to LCDs.

LDT is a joint venture between television maker Schneider AG and Daimler-Benz AG whose research team has roots in the former East Germany. It's betting the successful demonstration of its technology at last week's Internationale Funkaustellung (IFA) will attract licensees for its heavily patented system. Progress toward a product has been slower than expected, and no licensees have yet been announced for the technology.

But observers at IFA said the display looks better than most other projection-based displays. Indeed, the gamut of colors available is wider than either film or television phosphors provide. While LDT has developed conventional digital inputs, the red, green and blue balance must be remapped internally to produce natural-looking scenes.

The primary advantage of the laser display is that the quasi-parallel laser beams need not be focused onto a screen. The image can thus be projected over large distances onto the side of a building, for example.

Holger Frost, a scientific technical assistant at LDT, said the system uses a diode-pumped solid-state laser operating at infrared wavelengths. Multiple outputs are shone through a crystal with non-linear optical properties to produce frequency doubling to the visible spectrum. Mixing of different outputs produces red light at 635 nm, green at 532 nm and blue at 447 nm.

LDT uses conventional electro-optic modulators to turn the red, green and blue lasers on and off. A rotating polygonal mirror and oscillating mirror achieve line and vertical deflection of the beam, Frost said.

"The laser unit measures about 1.8 x 0.8 x 1.2 meters, but that is mainly due to transformers and compressors for the main laser. We could certainly reduce size to go on a desktop," Frost said.

Frost also said LDT had taken first samples of silicon micromirrors. Those could be used to create a smaller deflection unit for beam-raster scanning.

Texas Instruments Inc. produces similar devices that employ an electrically addressable array of micromirrors to form an image, with each mirror defining a pixel in the final image. But the LDT system cuts the mirror count to two--one each for the vertical and horizontal scanning.

Frost declined to name the source of the device silicon, which LDT says was produced under contract.

Free Subscription to EE Times First Name Last Name Company Name Title Email address   Click here for your Free Subscription to EETimes Europe