Display Week 2009 Review: Projection
Pico projectors begin to come of age, and new projection technologies appear as well.
by Alfred Poor
IN RECENT YEARS at the annual SID Symposium, front-projection technology has played a shrinking role compared with that of flat panels and related components. Even so, a broad range of demonstrations and research results provided a rich resource for those interested in projection. The biggest buzz at this year's show was the rapidly evolving pico-projector market segment.
Pico projectors are devices small enough to be incorporated into a typical mobile phone or similar portable device. With device volumes measured in single-digit cubic-centimeter sizes, this product segment is just coming to market in significant quantities, but much work continues to be done on components, from light sources to imagers. Some of the areas of investigation include increasing light output, reducing or eliminating speckle from laser light sources, and decreasing power consumption.
Corning demonstrated its G-1000 solid-state green laser that draws about 60 mW, suitable for compact projection devices. The laser uses optical frequency doubling to convert output from an infrared laser to obtain green light. The company has a reference design board that includes the laser and has already announced an agreement to provide green lasers to Microvision for its pico-projector products. The green laser is an important development for pico-projector applications. While red and blue compact lasers have been readily available, devices have had to rely on alternate sources of green light, such as LEDs, which are limited in terms of light output and light management. Corning expects to have the G-1000 in commercial production by the end of 2009 (Fig. 1).
OSRAM presented a paper on a compact RGB laser module (20.4: "Compact RGB Laser Module for Embedded Laser Projection") that combines the lasers with a driver ASIC and optical components. The device can be contained in a 7-mm-tall package that measures just 6.5 cm3.
Fig. 1: Corning demonstrated a prototype controller board with its green laser (rectangular component at top left).
3M also presented a paper on its new MM200 mobile projection engine. Using a color LCOS imager and a white-LED light source, the device is rated at 8 lm at 1-W LED power. The VGA resolution (640 x 480) engine has an external volume of just under 14 cm3. For complete devices, Microvision showed its new SHOW WX pico projector that is scheduled to ship this summer. The wide-VGA resolution (848 x 480 pixels) image is rated at much more than the existing color space used in TV today. It is rated at 10-lm light output and is designed to be able to show an entire movie on a single charge of its internal battery. Micron also demonstrated a prototype pico-projector device with wide-quarter-VGA (WQVGA) resolution using an imaging panel based on the recently acquired ferroelectric liquid-crystal–on–silicon (FLCOS) technology from Displaytech. This allows memory, image processing, and light-driver control to be incorporated into one chip along with the display panel itself, resulting in a compact device (Fig. 2).
Texas Instruments showed an example of a new Samsung personal media player scheduled to ship in Korea that includes an embedded pico projector using TI's 0.17-in. HVGA DLP chip. This chip, the 2009 SID/Information Display Display of the Year Silver Award winner, is now also available in a DLP Pico-Projector Kit using LED illumination resulting in a 7-lm-rated output; the kit is compatible with Beagle Board for system development (Fig. 3).
New Approaches
A variety of novel projection technologies was presented at Display Week. One of the most intriguing of these was covered by a paper and a poster presented by researchers from the University of Washington, which described a scanning optical-fiber projection engine for pico projectors. The tip of a single optical fiber is vibrated to create a scanning image. The piezoelectric vibrating device, fiber end, and optics can be fit into a 1-mm-diameter package that is 9 mm long. The fiber can transport the output from RGB light sources and the modulating circuitry. The angle of the tip's deflec-tion can be adjusted electronically, which in turn controls the "throw" of the projector without the need for any zoom-lens optics. The poster reported throw angles ranging from 20° to 100°, simply through adjusting the voltage applied to the piezoelectric component.
Fraunhofer IPMS demonstrated a tiny MEMS array that is designed for a raster scan image with small dimensions that can be used for laser projection. The array can scan a line at a time, as contrasted with a single-pixel device that has to be scanned horizontally and vertically to create an image or with a matrix panel that can create a complete image at one time. Thenew device can achieve a 10° deflection with a 1-msec response time. According to a Fraunhofer IPMS representative, the same technology could be used to create a full-image panel.
The Big and the Small
Novel technologies were presented for both big and small front projectors. Fraunhofer IPMS presented a paper describing a projection system using an OLED panel as both the imager and the light source. Optics can project the image onto a small screen, with applications ranging from a head-mounted system to pico projectors in mobile devices.
At the other end of the size range, Christie Digital Systems presented a paper that addresses the problem of laser speckle for large projectors such as those used in digital cinema. By "piping" the light from the image to the projection optics along a fiber-optic cable, the coherence of the light beam is reduced to the point that speckle can no longer be observed. This has the added benefit of separating the lasers from the projection head, which can simplify the system installation. This was just one of several papers and technology demonstrations that illustrated the significant progress that is being made at reducing the speckle that can be a distraction for laser-illuminated displays.
In short, while projection technology did not take a front-row position at Display Week 2009, there was enough new technology and reports of advances to warrant our keeping an eye on the big (and small) screens. •
Fig. 2: The prototype pico projector by Micron used the Displaytech FLCOS technology to create an image that was both large and legible, even in the exhibit hall at Display Week 2009.
Fig. 3: This new personal media player from Samsung is intended for the Korean market and includes an embedded pico projector based on the TI chipset.