Eyes off, screen off
Technology Research News
If a computer screen is on, but no one
is watching, it still consumes energy.
Researchers from Duke University have devised a detector that
determines if a person is present and looking at a computer screen, and
keeps the screen on only when it is being watched.
The key to making a practical power-saving detector was making
sure that the device itself used very little energy, said Angela Dalton,
a researcher at Duke University. "There had to be very low power sensors,
and algorithms that could be simplified enough that the system did not
use more energy in overhead than it saved," she said.
The researchers' prototype uses a wireless motion sensor and a
WebCam. When the motion sensor is triggered, indicating that someone is
present, the WebCam turns on and takes pictures, and the pictures are
analyzed by a face detection algorithm to determine if anyone is looking
at the display.
The system, dubbed FaceOff, consumes almost no power when waiting
for the motion sensor to trigger, and the camera consumes between 1 and
1.5 watts when it is running, said Dalton. In an initial study, the system
achieved energy savings as high as 30 percent, she said.
The system uses off-the-shelf parts, and could be optimized to
consume even less power, said Dalton. Tiny cameras that can be embedded
into computer systems and consume as little as 20 milliwatts, or thousandths
of a watt, could further increase energy savings, according to Dalton.
Face recognition software that triggers a screen saver is available
commercially as an extra in security applications that identify authorized
users, but these packages don't go so far as to track gaze.
The Duke prototype "shows the feasibility of using low-power sensors
to better match system input-output behavior to user behavior, and by
doing so reduce overall system energy consumption," said Dalton.
With the increasing availability of cheap, low-power sensors,
numerous mobile devices could use this kind of technique to reduce energy
consumption and thus extend battery life, according to Dalton. Mobile
devices with built-in sensors, including cameras, microphones, light sensors,
and global positioning system receivers are becoming available. "Mobile
devices could leverage the sensors beyond their obvious uses to determine
user intention and context, and match the system behavior," she said.
The researchers' work is a twist on traditional system-level energy
management, which has historically been tied to turning components off
when they are not engaged. Input-output devices, however, might be needed
by the user even if the computer is not carrying out a process. At the
same time, computer displays account for a relatively high percentage
of computer power use.
A 17-inch cathode ray tube monitor, for instance, draws between
60 and 120 watts, and even flat panel monitors draw between 15 and 25
Practical energy-saving sensor systems could be implemented in
two to three years, according to Dalton.
Devices are capable of performing the necessary computation, and
the types of sensors the systems will require currently are available,
she said. "The main hurdle [is] user studies to determine usability, usage
scenarios, and user interface requirements."
The researchers' next step is to perform a comprehensive user
study to better characterize the scenarios in which the technique is useful,
said Dalton. The researchers are also planning to experiment with how
often to sample the users gaze, to, for example, make the system more
responsive when motion is detected and decrease or halt image sampling
when no motion is detected, according to Dalton. And they are planning
to incorporate a light sensor into the prototype so the display brightness
can be adjusted to save power.
Dalton's research colleague was Carla S. Ellis. They presented
the work at the Usenix HotOS IX: 9TH Workshop on Hot Topics in Operating
Systems in Lihue, Hawaii, May 18 to 21, 2003. The research was funded
by the National Science Foundation (NSF).
Timeline: 2-3 years
TRN Categories: Human-Computer Interaction
Story Type: News
Related Elements: Technical paper, "Sensing User Intention
and Context for Energy Management," presented at Usenix HotOS IX: 9TH
Workshop on Hot Topics in Operating Systems, Lihue, Hawaii, May 18-21,
2003, and posted at
July 30/August 6, 2003
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