Palm-sized 'pico-projector' enabled by MEMS

PORTLAND, Ore. -- Digital projectors revolutionized mobile presentations by harnessing mass-produced liquid-crystal display (LCD) technology to stand-in for viewgraphs--enabling high-output light bulbs to shine through the LCD instead of through plastic sheets. While digital-projector companies progressively downsize their LCDs, making units smaller and lower power, digital micro-mirror technology stands poised to leap-frog digital projectors down to cell-phone size.

At this year's Consumer Electronics Show (CES, Las Vegas, Jan. 7-10, 2008), Microvision Inc. (Redmond, Wash.) will be showing a prototype of its pico-projector, which uses micro-electro-mechanical systems (MEMS) to downsize a digital projector to a palm-sized battery-powered unit.

Texas Instruments has been privately showing a cellphone-sized prototype of its digital-light projector (DLP), which uses a MEMS chip with a million micro-mirrors to project images. Now, Microvision claims to have downsized the pico projector by replacing TI's million-mirror MEMS chip with its own single-mirror MEMS chip, which Microvision claims can be produced cheaply enough to become standard equipment on future cell phones.

"Our MEMS chip is fundamentally different [from TI's DLP]," said Russell Hannigan, senior product marketing manager at Microvision. "TI's DLP dedicates a separate mirror to each pixel, requiring a million micro-mirrors for a million-pixel display. Instead, we use a single mirror to create all the pixels--enabling our device to be much, much smaller and less expensive."

Microvision's pico-projector won last year's innovation award for consumer electronics devices from Frost and Sullivan Research. Microvision has already signed up a few customers: Motorola's Mobile Devices division, for its handheld projector modules; an unnamed automotive supplier for in-vehicle use of its pico-projector; and an unnamed Asian "large consumer electronics manufacturer," for cell phones, digital cameras and personal media players. The company promises to announce new OEM deals in 2008, when it begins delivering its first modules to customers.

Decade in development

Almost a decade in development, Microvision's MEMS-based pico-projector is based on a unique MEMS technology platform that makes use of laser scanning technologies borrowed from Microvision's successful bar-code reader product. Solid-state lasers combined in the same tiny module with a single digital micro-mirror simplify the whole projection system by not requiring any optical lenses. Control circuitry aims the lasers in a raster-scanning pattern, modulating its coherent beam onto each pixel of the display by moving the single mirror to keep the image in focus regardless of distance.

"We arrange it so the image is always in focus--with no need to adjust it with a lens--from about 200 millimeters [8 inches] to maybe two meters [80 inches] away, so you can literally move the image from the wall to the ceiling and it will always be in focus," said Hannigan.