Imagine that your mobile phone or PDA had a display the size of a laptop's but still fit snugly in your pocket. Hardware engineers at several companies are working on miniature video projectors that promise just that. Using projection, "you can make an image larger than the size of the device you carry," says research scientist Ramesh Raskar of the Mitsubishi Electric Research Laboratories in Cambridge, MA.

Key to the new projectors are lights small enough to squeeze into a PDA-sized gadget but bright enough to display crisp images. Lumileds Lighting in San Jose, CA, has built a prototype projector roughly the size of a pocket camera that employs small, powerful light-emitting diodes (LEDs) to throw an image the size and brightness of a laptop's screen onto any white surface. The Mitsubishi lab is using LEDs to build an even smaller projector, about the length and width of a credit card.