High-Definition TV from your Cell Phone

New MEMS technology could lead to dime-sized, high-resolution projectors


A silicon mirror suspended by carbon fibers can vibrate very quickly, scanning a laser across a surface fast enough to draw high-resolution images.
A cell phone that can project a high-definition television image could soon be possible, say researchers at Cornell University who have developed a new microelectromechanical system (MEMS) for rapidly scanning wide areas with a laser. A projector based on the device would be about the size of dime and could cast a meter-wide image on a surface only half a meter away.
The key is a small mirror, about half a millimeter across, suspended by carbon fibers — rolled-up sheets of crystalline carbon commonly used to reinforce materials. The fibers amplify the vibrations of a piezoelectric motor, moving the mirror. This movement deflects a laser at different angles, causing it to sweep back and forth across a surface. While the current device only moves the laser side to side, the researches say it can be easily mounted on a stage that tilts up and down to allow the device to sequentially draw each line of an image, using complex electronics that turn the laser on and off as it is directed across the screen to create the light and dark pixels. A full-color display would mix light from red, green, and blue lasers


Ming Wu, an electrical engineering and computer science professor at the University of California, Berkeley, says that in addition to high scanning speeds, the resolution of an image depends on the size of the mirror used. In the past, he says, mirrors large enough to produce high-quality images, on the scale of a few millimeters across, have been a challenge: it’s difficult to make the mirrors vibrate fast enough without breaking the apparatus. Thompson says the tough carbon fibers have allowed them to use a mirror half a millimeter across, already about the size-scale needed. He adds that by using more carbon fibers, the Cornell researchers expect to be able to increase the size even more