TechBlog

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.

The single mirror scans from pixel-position to pixel-position like a cathode-ray tube, but instead of using an electron beam it uses red-, blue- and green-lasers. As a result, there is no focusing lens required, because the lasers already render razor-sharp points without external optics. This enables the full spectrum of colors and shades of gray to be illuminated on a million pixel display by a pico-sized projector that’s seven millimeters thick and taking up just five cubic centimeters of total volume.The mirror itself is round, about one-millimeter in diameter, and is deflected in both the x- and y-planes simultaneously. As the mirror scans left-to-right and top-to-bottom, the three-lasers are modulated so that each pixel in the display receives the appropriate mixture of red, green and blue light to render a scene accurately.

The main disadvantage of Microvison’s pico-projector is that it only has a brightness of about 10 lumens–compared with 100 lumens or more for suitcase-sized digital projectors offered today. However, the pico-projector also uses much less power than today’s competing technologies, because it does not depend on constantly-on high-intensity light bulbs.

“Our device is much lower in power–typically half the power of our competitors,” said Hannigan. “With a DLP, for instance, the light source must always be on, but our light source is only on when we need it, which is incredibly important for battery-powered devices.”

Microvision will be showing its pico-projector to select OEMs at the CES in its private suite. The palm-sized unit will have 2.5 hours of battery life when released in mid-2008, but the prototype shown at CES will only achieve about 1.5 hours of battery use. The prototype uses a widescreen, WVGA (848 X 480 pixels), format for DVD-like quality images.

“You really need to see the DVD-quality of our image in a two- to four-inch format to appreciate how good it looks,” said Hannigan.

Microvision said they expect customers to use its pico-projector in locations where other small projector technologies are too bulky and power-hungry–such as watching YouTube videos while sitting in bed, or MSN newscasts at the breakfast table, or to project PowerPoint presentations on a cocktail napkin at lunch. For portable media players, the unit will provide enough battery life to watch a complete feature-length film on a plane.

The company expects the unit to be initially offered in stand-alone portable projectors you attach to an iPod during 2008, but by 2009 it also expects OEMs to begin incorporating the five cubic centimeter unit into cell phones and portable media players.