For several years people have been talking about the idea of miniaturizing a projector so that it's small enough to fit inside a cell phone or digital camera. Now it's finally been done, and 3M is demonstrating a prototype of such a device at this year's International Consumer Electronics Show.

The mobile projector is about a centimeter thick and about 4 centimeters tall by 3 centimeters wide -- small enough to fit inside portable devices like cell phones, PDAs, or a digital still camera, said Todd Rutherford, product development specialist with 3M's optical systems division.

It uses an LED as the light source and can project a VGA resolution (640 pixels by 480 pixels) image through a lens that's about a centimeter in diameter.

3M is demonstrating the projector at CES built into a small handheld device that runs video from flash memory. The image projected onto walls or other light surfaces was good enough and easy enough to see over a distance of about half a meter, although it suffered over greater distances due to the bright lights of the show floor.

The demo attracted a lot of attention and a constant stream of show attendees, many of whom had badges identifying them as employees of mobile phone makers or network operators.

3M is already working with companies interested in embedding the projector in devices, and the first products should be out in early 2008, said Rutherford. He wouldn't identify the companies or the applications but said that they are mobile consumer electronics products.