E-book readers with black-and-white screens look like they’re stuck in a time warp, now that Apple’s full-color iPad is on its way.
But not for long. A new generation of displays are waiting to bring full color and video to low-power displays, while maintaining readability in different environments. That’s something that Apple’s LCD-based “Moses tablet” — and E Ink’s low-power, monochrome screens — can’t do.
One of the e-reader hopefuls is Qualcomm, whose latest technology, named Mirasol, promises to combine color, speedy refresh rates and low power consumption in a single display. Qualcomm hopes to have the first color screens available in e-readers by fall this year.
“For e-readers users coming from a black-and-white world, this is going to be like ‘Oh, my prayers have been answered’,” says Cheryl Goodman, director of marketing for Qualcomm.
With an estimated 5 million sold last year, e-readers have become one of the fastest-growing consumer electronics categories. And while screen sizes and functionality may be different, they all have one thing in common: Almost all of them use a black-and-white display from E Ink, the company that pioneered the low-power technology. The reason that e-readers like Amazon’s Kindle, the Sony Reader and the Barnes & Noble Nook can go days or even weeks without a recharge is that they use power only when the screen changes. In between, while you’re reading the page, the screen draws no power because its pixels are “bistable” — they have two stable states, dark and light, and can remain in either state without drawing power.
But the iPad’s debut and its focus on e-reading has raised the stakes for Amazon and other entrants. Amazon has reportedly acquired Touchco, a company that could provide it with the technology to add a touchscreen to the Kindle. A push for a color display would likely come with any new product that would use the Touchco tech.
Qualcomm’s Mirasol could be one of the contenders. Mirasol displays work by modulating an optical cavity to reflect the desired wavelength of light. The reflected wavelength is proportional to the cavity’s depth.
And if you are wondering what a color low-power Mirasol screen looks like, think a glossy scientific textbook rather than an LCD screen. It’s subdued, somewhat low-contrast, but crystal clear. Its reflective surface means that it doesn’t have (or need) a backlight. Its pixels, like E Ink’s, are bistable, so it will draw power only when refreshing the screen. And it can play video.
“It’s a very good display for what it does, which is an extremely low-power color screen,” says Vinita Jakhanwal, an analyst with research firm iSuppli.
Color screens for e-readers are more than a question of aesthetics. Many genres of books, including textbooks, cookbooks and comics, require color illustrations to make them come alive. Magazines and even newspapers are rendered almost unrecognizable without color.
Low-power color displays could change that. They could also help convince reluctant consumers to get a gadget designed for reading, without giving up gains in battery life.
A 5.7-inch Mirasol screen, not much bigger than an index card, with a resolution of 1024 x 768 pixels, can offer at least five times the battery life of a 6-inch Kindle black-and-white Kindle display, says Goodman. The 5.7-inch screen is the size that Qualcomm is planning to debut its color displays in, though it says it can do larger screen sizes based on demand.
Mirasol displays are built on glass substrates. Thin films deposited on the substrate form one wall of the cavity, while the other wall is a highly reflective flexible membrane. An electric force applied across the cavity causes the membrane to collapse against the thin films. The cavity then becomes very thin, and the wavelength that is reflected moves into the ultraviolet spectrum.
For the viewer, this element, which is one pixel, is seen as black. Varying the depth of the cavity results in changes in the wavelengths reflected, which yields different colors.
“Because you use the lighting around to generate the image and color, it makes the display extremely low power,” says Jim Cathey, vice president of business development for Qualcomm.
And like the E Ink display, it is visible even in bright sunlight.
“Mirasol does color well but it has difficulty in reproducing gray scales,” says Jakhanwal. “When it comes to black-and-white, it is not as high contrast as an E Ink screen, but the advantage Qualcomm has is that it can offer color now.”
The 5.7-inch color Mirasol screen is bigger than the iPhone's, but not by much.
A Nascar race on the Mirasol display may not be pleasant, but the screen’s refresh rate of up to 24 frames per second is good enough for almost every other kind of video. In a demo at Wired.com, the screen showed a decent, sub-second refresh rate that was noticeably slower than 24 fps, but fast enough to show slow-motion moving images of butterflies.
Mirasol’s response time is also better than E Ink — in microseconds, compared to E Ink’s 200 or so milliseconds.
Still, many customers could find the videos on a Mirasol display unappealing, says Jakhanwal.
“Videos look much better in Mirasol than they do in E Ink,” she says. “But when you are watching video you want full color saturation and a washed-out picture is not that attractive,” she says.
Convincing e-reader manufacturers to bet on Mirasol won’t be easy. Qualcomm will have to compete against Pixel Qi, a scrappy California-based startup whose displays combine a full color LCD screen with a low-power black-and-white display. And then there’s E Ink, the current market leader that promises to come out with color displays by the end of the year.
Mirasol’s success will also depend on Qualcomm’s ability to prove that it can manufacture millions of displays that its customers will need. After all, Qualcomm is a chip company that’s known for creating processors that power smartphones, not displays. The Mirasol technology comes to the company through its acquisition of Iridigm Display five years ago.
Qualcomm says it’s serious about creating a place for itself in the display business. The company has set up a fabrication plant in Taiwan dedicated to producing Mirasol displays.
“Taking it from the lab to the fab is the tough part,” says Goodman. “But we have launched Mirasol on a few phones.” In 2008, one of the first handsets, the HiSense C108, featuring a black-and-white Mirasol display, debuted in China.
For the color screens, though, Qualcomm is betting on e-readers.
“The challenge in the e-reader market is that there are a lot of substitutes — the iPhone, laptop or the iPad,” says Qualcomm’s Cathey. “But we think consumers want color content and long usage between charges in a variety of environments.”
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Photos: Jon Snyder/Wired.com
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