Turning red to green is a lot harder than it sounds.
It also might be the ticket to making portable video more watchable.
More companies are promising compact projectors designed to ensure that, once you download the latest feature film onto a portable video player or phone, the viewing experience isn’t devalued by the device’s tiny screen size. Instead, the video can be projected on a wall or screen for a viewing experience more akin to watching television or going to a movie theatre.
One of the light-emitting components that technologists would like to use in these projectors — green laser diodes, which are brighter than the more common red laser diodes — is relatively difficult to make in a configuration that uses modest amounts of electrical power. But at least a couple companies are intent on refining the technology enough to improve its commercial viability.
Turning handheld devices into projectors isn’t a new concept, but several challenges have persistently gotten in the way. To fit inside a standard mobile phone today, a projector can occupy no more than four to six cubic centimetres of space. Some companies have managed to make that happen, but then bumped into another problem: price. Though manufacturers aren’t saying specifically how much these tiny projection devices will cost, the smallest projectors on the market today retail for under US$1,000.
At the Society for Information Display 2007 conference in Long Beach, California, last week, executives from glass and ceramics specialist Corning discussed their company’s green laser diode, which it is selling to customers to put inside tiny projectors. Corning announced that Microvision, a maker of miniscule mobile projectors, will use Corning’s green laser diode in its PicoP projector. Microvision says its projector will enable wide-screen, DVD-quality viewing image in a projector less than 7 millimetres thick. Though it’s not available for cell phones or media players quite yet, it’s one step closer.
“Green laser diodes will be great when they arrive, is the bottom line. Lasers and projections systems are a natural pair,” said Matthew Brennesholtz, analyst at Insight Media. “The problem today is lasers are far too expensive — a hundred times too expensive — to use in a consumer product.”
Beyond LEDs
That’s what Corning and Novalux, the other major player in green laser diodes, are trying to accomplish, according to Brennesholtz. “There’s not a fundamental physical barrier to making a reasonably priced laser. They’ve got to get the supply chain in place, get the customers, set up the projection lines, grow the crystals,” he said.
Prices will come down over time, and then green lasers run into another challenge: Before they can be put into cell phones the projectors have to draw as little charge as possible off the battery. A phone is made for communicating, and if a secondary activity, like watching a movie, drains the batteries after an hour, having the extra capability won’t be worth it to consumers or manufacturers.
For now, there’s another option. LEDs (light-emitting diodes) have been used as an alternative light source for projectors by others, such as the Finnish company Upstream Engineering. But LED-based projectors tend to be less bright and aren’t an efficient source of light. The attraction to LEDs is their low power requirements, but lasers are catching up. Texas Instruments uses its own DLP (digital light processing) technology in a prototype mobile projector, which it also displayed at the Consumer Electronics Show earlier this year.
Cell phone makers want just one watt of battery power to be devoted to projection capability, but even the tiniest laser projectors typically draw two to three watts right now, according to Brennesholtz. “They have to increase their efficiency before we see any integrated” into projectors, he said.
Corning and Novalux have both spent years refining the process of creating a green laser diode. To make a full-colour image, you need red, green and blue. Red lasers have been used for two decades to read CDs, and though blue lasers are newer, there are plenty of blue-laser manufacturers that supply the lasers for next-generation DVD players, such as those using Blu-ray high-definition DVD technology.
Green lasers are harder to create and maintain because they are unstable, meaning they die after only a few hours. The solution is to start out with the laser diode a different colour, such as red, and change it to green by adjusting its frequency.
An optical path to green
In this case, Corning uses an optical process to create green. Corning’s green laser diode will take up only about one cubic centimetre of space and is made to operate inside projectors that will put out 10 to 20 lumens of brightness — equivalent to what an LCD monitor gives off — to project an image that measures 9 to 12 inches (23cm to 30.5cm) diagonally. The picture can be made bigger — enlarged to, say, 60 inches — but moving a projector farther from a screen or wall also decreases the brightness.
“The neat thing about projectors is if you’re willing to make the room dark you can make a 60-inch diagonal image and it looks OK,” said James Grochocinski, the product line manager for Corning’s green laser program.
Of course, it’s not exactly clear what the demand for pocket-size projectors are, and many analyst firms don’t even keep data on them. Toshiba and Mitsubishi are among the few companies that make projectors that weigh less than a pound.
“I’m not sure people know those kinds of products exist. They tend to not have as good resolution or be as bright as LCD-based projectors,” said Stephen Baker, vice president of industry analysis for The NPD Group. “Most of these are based on LEDs. Usually 800-by-600 resolution, not as great as what you’ll get by spending a little bit more and getting a bigger product.”
Which could well mean it will be that much longer before we see projectors integrated into devices such as mobile phones. In the meantime, projectors that are half the thickness of a deck of cards and suitable for sharing pictures and video probably won’t be available on a large scale until 2008.
“There were half a dozen demonstrated at [the Consumer Electronics Show]. How long it takes to go from a demonstration to a product” is something else, said Brennesholtz. “Assuming someone took it up at CES and committed, it would still probably take them 18 months to turn it into a product. Maybe a few by Christmas, but not mass volumes. We’re probably talking some time.”
