on. However, now eye-tracking developers are tackling the really difficult work--making the technology efficient for general business applications.
Some benefits of eye tracking are obvious. Lab studies have shown that the technology lets you work about 25 percent faster than you can with a traditional mouse. Hands-free input also means no carpal-tunnel problems or tendinitis. What's more, eye tracking may be the only way for some disabled people to interact with a computer.
But researchers have their eyes on even bigger prizes. Some people think eye tracking is ushering in a new era of
noncommand interfaces
that engage computers and humans in a continuous dialogue. Rather than waiting for you to issue discrete commands, these interfaces monitor body language to anticipate your next move, like a bass player accompanying a jazz pianist.
Eye tracking can be especially useful when you're b
rowsing for information, whether it's application icons scattered across a screen or hot links throughout a Web document. However, the mouse will still reign once you're in a document and performing precise tasks, such as cutting and pasting.
When everything's going right, says Robert Jacob, an eye-tracking researcher since 1988, eye tracking feels like "the system is executing the user's intentions before he or she expresses them." But not everything works right all the time. Although commercial eye-tracking hardware has dropped in price from about $250,000 to $20,000 in the last eight years, the hardware can be unstable. A system that works well with one person might stumble when someone else sits at the computer. One explanation: People with naturally larger pupils have the greatest success with eye tracking.
That's because the pupil is the command center for most eye-tracking systems. Eye-tracking hardware shines an infrared beam into the user's eye to illuminate the pupil so that a custom v
ideo camera mounted on the computer can record the pupil image. Image-processing hardware digitizes the pupil image and turns eye movements into horizontal, vertical, and depth coordinates.
During the dark ages of eye tracking, humans had to use a bite bar to make sure their heads didn't move. Today's systems factor out head movement by reading a nonpupil reference, typically a point of light reflected from the cornea.
Hardware vendor ISCAN sells systems that consist of two AT-bus cards that plug into a standard PC or workstation and handle coordinate tracking and image processing (see the figure
"Eye-Tracking Hardware"
). A video camera with infrared optics to capture the user's eye image can be mounted on the PC or attached to a lightweight headband. The headband includes a special mirror that the user can see through but reflects an infrared beam into the user's pupil; a cable connects the headband directly to the image processors in the PC.
Applied Science Laborat
ories sells similar systems. The company recently purchased technology from Daimler Benz, which has developed systems that can be used in bright-light conditions.
The basic hardware components of a rudimentary eye-tracking system are becoming commonplace on today's PC. For example, some PCs and Power Macs now ship with a video camera, built-in frame grabbers, and high-speed video processors. This equipment would need customization for eye tracking--video cameras for eye tracking require stronger telephoto capabilities than videoconferencing requires, for example--but the basic building blocks are there.
Eye-tracking hardware is only half the puzzle. Software will be the key to turning this specialized equipment into a workable input system for business applications. A key software component is the user interface management system (UIMS), which interprets eye positions and monitors the areas on the screen where a person focuses attention. A fixation algorithm turns these pauses, known as
dwel
l time
, into a discrete token, which is eye-tracking parlance for
events
. "We report tokens for the start, continuation, and end of each detected fixation," says Jacob, who began developing UIMS software at the Navy Research Laboratory and has moved to Tufts University to continue his work. His UIMS is written in C++ and runs under Unix.
In practice, the interface screen might be filled with application icons. You'd need to focus on an icon for only 150 to 250 ms before the eye-tracking system interpreted that dwell time as a command and opened the application.
In some early systems, eye movements controlled an on-screen cursor. But researchers have discarded that approach because users became annoyed by a blurred arrow that was always flying around within their field of vision.
Users haven't reported such problems as eyestrain while using these systems. However, some older hardware needed an IR light so strong that it dried out the tears of people wearing contact lenses. Ot
hers say that the systems are so fast and responsive that they try to avoid blinking for fear of missing something.
Will eye tracking dominate our desktops by the turn of the century? Probably not. Vendors and researchers believe our eyes will be only one component of future "multimodal input" systems.
When those systems come, we'll be gazing, talking, and pointing at our computers to give them commands. And in return, our computers will become more adept at deciphering how our bodies say what's on our minds.
Where to find
Applied Science Laboratories
Bedford, MA
Phone: (617) 275-4000
Fax: (617) 275-3388
E-mail:
ASL@world.std.com
ISCAN, Inc.
Burlington, MA
Phone: (617) 273-4455
Fax: (617) 273-0076
E-mail:
iscan@cambridge.village.com
illustration_link (23 Kbytes)
Hands-free eye-tracking systems let people work 25 percent faster than they can when using a traditional mouse.
Alan Joch is BYTE's senior editor for features. You can reach him at
ajoch@bix.com
.
What Pupils Teach Computers
