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August 30, 2005

In Future, Ordinary Lights May Communicate, Boost Health

Some innovative ideas for using LED lighting.

By Malcolm Ritter

AP Science Writer

NEW YORK (AP) -- Scientists have been taking a closer look at the lighting in our homes, offices and vehicles, and they're seeing potential for a way to improve health and a new means of electronic communication.

None of this will happen tomorrow. But if you want a glimpse of where the field might be heading, listen to some experts at Rensselaer Polytechnic Institute in Troy, New York, an academic home for lighting research.

Start with engineer E. Fred Schubert, talking about a new era of "smart" light sources.

"We are looking at lighting systems that provide more than lighting," he says.

He's talking about light-emitting diodes, or LEDs. Most people know them as being quite small, like the lights that form numbers on digital clocks or blink on answering machines. But recent technological advances have made them much more powerful, able to illuminate swimming pools and serve as traffic signals, for example.

LEDs offer energy savings when compared to standard lighting, but Schubert is more excited about some other properties. One is that LEDs can be made to blink so fast that a person doesn't notice, but a receiving device can. And that, Schubert says, opens the door to using lights for electronic communication as well as illumination.

Of course, fiberoptic cables already transmit lots of data with light signals. But Schubert is talking about things like:

-- brake lights that tell a closely following car to stop, even if the driver doesn't notice.

-- headlights that tell a red stop light to turn green, if it's safe.

-- road signs that communicate warnings to specific cars.

-- room lights that link your computer to the Internet, avoiding Wi-Fi signals that can be pirated.

-- room lights that transmit messages to devices worn by only certain people, like particular doctors or nurses in a hospital, rather than speakers that spew announcements for everybody to hear.

Schubert said such uses depend on overcoming some basic technical barriers, like making LEDs more powerful and energy-efficient. "I think we're looking at maybe a timeframe of the next 5 to 20 years," he said.

Meanwhile, his Rensselaer colleague Mariana Figueiro believes that lighting in offices and schools could be improved to help people stay healthy and productive, by acting on their internal body clocks.

"Light isn't just for vision any more," says Figueiro, program director at Rensselaer's Lighting Research Center and head of a committee on light and human health for the Illuminating Engineering Society of North America.

The 24-hour internal body clock is best known for governing cycles of alertness and sleep, and for producing jet lag when people travel across time zones. Light cues, especially blue light, help keep the clock on its daily cycle. "We're pretty much blue-sky detectors" whose clocks count on bright days and dark nights, said Figueiro.

But that's not necessarily what modern life delivers. During the winter in the northeast, for example, a person can commute roundtrip in the dark and sit all day in electric light that's fine for vision, but may be too dim to stimulate the body clock. That's called biological darkness.

"We don't have this sharp signal of a bright light during the day and a dark night," Figuerio said.

How that affects people has been hard to document in the general population, she said, but studies suggest such possibilities as seasonal depression, fatigue, sleep disturbances and maybe even cancer, especially breast cancer. Some studies suggest reduced productivity on the job.

To counter that, architects and lighting engineers might someday take body clocks into account when they design lighting schemes, she said. They may be encouraged to take steps like providing plenty of natural light through windows and skylights, and installing bright blue LEDs near computer screens to give a dose of clock-adjusting light, she said.

David Sliney, a medical physicist who studies light-related issues at the U.S. Army Center for Health Promotion and Preventive Medicine, said research into how room lighting affects health is exciting but still in its early phases. It's not yet clear how it will affect lighting strategies, he said, but he believes it will.

George Brainard of Thomas Jefferson University, who studies the effect of light on the body clock, agrees.

Over the next two decades it will inspire engineers to look at "the redesign of virtually all human environments for lighting," he said. "There's no question in my mind about that."