Hello,

We noticed you're browsing in private or incognito mode.

To continue reading this article, please exit incognito mode or log in.

Not an Insider? Subscribe now for unlimited access to online articles.

Intelligent Machines

Energy-Saving Screens

Processors and memory chips keep growing in capacity, but batteries don’t improve fast enough to keep up. So the only way to increase the battery life of mobile devices such as PDAs and smart phones is to reduce the amount of power they consume. Working with a new generation of displays based on organic light-emitting diodes (OLEDs), researchers at Hewlett-Packard have found a way to do that: dimming the parts of the screen that aren’t in use.

“We have energy-aware central processors; why don’t we have energy-aware interfaces?” asks Parthasarathy Ranganathan, a senior research scientist at HP Labs. The prevailing approach to energy-saving displays – leaving the entire screen illuminated while a device is active but turning it off after a minute or two of inactivity – is less than ideal, since it uses a lot of energy when the screen’s on and, when it’s off, forces the user to push a button to return to his or her task. Instead, Ranganathan’s team developed special software that monitors a PDA’s screen when it’s in use and automatically dims the unimportant pixels – for example, everything in the background behind an active pop-up menu or dialogue box.

In studies with human volunteers, Ranganathan’s team found that Pocket PC devices equipped with the energy-saving software could last 1.3 to 8 times longer on a single charge than those without the software. Not only that, but “95 percent of our users preferred the new interfaces, even without the energy advantages,” Ranganathan says. “Deemphasizing low-interest areas means you’re emphasizing high-interest areas” – which seemed to help users focus on their immediate tasks.

This story is part of our December 2004 Issue
See the rest of the issue
Subscribe

The method is not effective with most of today’s standard liquid-crystal displays, which are illuminated by fluorescent bulbs that remain on even if a particular group of pixels is dark. But in OLED screens, each pixel emits its own light, so “if you turn off a pixel, you don’t have to spend power on it,” explains Ranganathan. Since phones and PDAs with OLED screens are expected to become commonplace within two years, the new software could soon be a standard feature of the operating systems of mobile devices.

Tech Obsessive?
Become an Insider to get the story behind the story — and before anyone else.

Subscribe today
More from Intelligent Machines

Artificial intelligence and robots are transforming how we work and live.

Want more award-winning journalism? Subscribe to Insider Plus.
  • Insider Plus {! insider.prices.plus !}*

    {! insider.display.menuOptionsLabel !}

    Everything included in Insider Basic, plus the digital magazine, extensive archive, ad-free web experience, and discounts to partner offerings and MIT Technology Review events.

    See details+

    Print + Digital Magazine (6 bi-monthly issues)

    Unlimited online access including all articles, multimedia, and more

    The Download newsletter with top tech stories delivered daily to your inbox

    Technology Review PDF magazine archive, including articles, images, and covers dating back to 1899

    10% Discount to MIT Technology Review events and MIT Press

    Ad-free website experience

/3
You've read of three free articles this month. for unlimited online access. You've read of three free articles this month. for unlimited online access. This is your last free article this month. for unlimited online access. You've read all your free articles this month. for unlimited online access. You've read of three free articles this month. for more, or for unlimited online access. for two more free articles, or for unlimited online access.