An Alternative to the Computer Mouse
A user interface that tracks eye movement may provide
an alternate way to use a computer.
Technology Review
By Kate Greene
The eyes have it: Logo from the Gaze-enhanced User
Interface Design (GUIDe) project at Stanford. The
projects goal is to use information about where a
person is looking in order to develop applications
that make interacting with computers easier.
Credit: Manu Kumar, the GUIDe Program at Stanford
University Multimedia
A researcher at Stanford has created an alternative to
the mouse that allows a person using a computer to
click links, highlight text, and scroll simply
by looking at the screen and tapping a key on the
keyboard. By using standard eye-tracking hardware--a
specialized computer screen with a high-definition
camera and infrared lights--
Manu Kumar
, a doctoral student who works with computer-science
professor
Terry Winograd
, has developed a novel user interface that is easy to
operate.
"Eye-tracking technology was developed for disabled
users," Kumar explains, "but the work that we're doing
here is trying to get it to a point where it
becomes more useful for able-bodied users." He says
that nondisabled users tend to have a higher standard
for easy-to-use interfaces, and previously,
eye-tracking
technology that disabled people use hasn't appealed to
them.
At the heart of Kumar's technology is software called
EyePoint
that works with standard eye-tracking hardware. The
software uses an approach that requires that a person
look at a Web link, for instance, and hold a
"hot key" on the keyboard (usually found on the number
pad on the right) as she is looking. The area of the
screen that's being looked at becomes magnified.
Then, the person pinpoints her focus within the
magnified region and releases the hot key, effectively
clicking through to the link.
Kumar's approach could take eye-tracking user
interfaces in the right direction. Instead of
designing a common type of gaze-based interface that
is controlled
completely by the eyes--for instance, a system in
which a user gazes at a given link, then blinks in
order to click through--he has involved the hand,
which makes the interaction more natural. "He's got
the right idea to let the eye augment the hand," says
Robert Jacob, professor of computer science at
Tufts University, in Medford, MA.
Rudimentary eye-tracking technology dates back to the
early 1900s. Using photographic film, researchers
captured reflected light from subjects' eyes and
used the information to study how people read and look
at pictures. But today's technology involves a
high-resolution camera and a series of infrared
light-emitting
diodes. This hardware is embedded into the bezel of
expensive monitors; the one Kumar uses cost $25,000.
The camera picks up the movement of the pupil
and the reflection of the infrared light off the
cornea, which is used as a reference point because it
doesn't move.
Even the best eye tracker isn't perfect, however. "The
eye is not really very stable," says Kumar. Even when
a person is fixated on a point, the pupil jitters.
So he wrote an algorithm that allows the computer to
smooth out the eye jitters in real time. The rest of
the research, says Kumar, involves studying how
people look at a screen and figuring out a way to
build an interface that "does not overload the visual
channel." In other words, he wanted to make its
use feel natural to the user.
One of the important features of the interface, says
Kumar, is that it works without a person needing to
control a cursor. Unlike the mouse-based system
in ubiquitous use today, EyePoint provides no feedback
on where a person is looking. Previous studies have
shown that it is distracting to a person when
she is aware of her gaze because she consciously tries
to control its location. In the usability studies that
Kumar conducted, he found that people's performance
dropped when he implemented a blue dot that followed
their eyes.
In his studies of 20 people, he found that
participants that needed to type and point could point
faster using the gaze-based appraoch than using a
mouse,
although the error rate--20 percent--was fairly high.
But overall, about 90 percent of participants reported
that they preferred using EyePoint to the
mouse.
It's the 20 percent error rate that could cause some
problems, says
Ted Selker
%7Eselker
, professor at the MIT Media and Arts Technology
Laboratory. "[It's] a huge amount," he says, "because
a person can notice a significant decline in accuracy
at just 5 percent." Selker adds that the low accuracy
could make text editing a challenge.
Kumar concedes that the system isn't perfect, but he
contends that many of the errors came from people, who
due to lack of practice, clicked links that
they thought they had looked at but were only in their
peripheral vision. Indeed, he says, trackpads,
trackpoints, trackballs do not perform as well as
a mouse either but are still viable input devices.
Kumar says he's been working on algorithms that show
promise for making EyePoint more accurate by
accounting
for peripheral vision related errors. Still, he allows
that EyePoint might work poorly for certain people,
such as those with thick glasses, special contact
lenses, or lazy eyes.
Even so, Kumar is confident in the technology and its
development as a tool for the general population. To
that end, he has tested a number of different
interface schemes, all under a project called
Gaze-enhanced User Interface Design
(GUIDe). Another application, called EyeExposé, is
made for Apple's OS X feature called Exposé, in which
a person can hit the F11 key to miniaturize all
open windows, then drag the mouse cursor to the window
she wants to bring forward. With EyeExposé, the user
can hit the F11 key, then bring forward a window
of interest by tapping a keyboard key. Also, Kumar has
modified the "scroll lock" key on a keyboard in an
application called EyeScroll: as a person reads,
the screen slowly reveals more text. In addition,
Kumar is testing a modified version of the "page up"
and "page down" keys. When a person reads to the
bottom of a page, the software automatically scrolls
down one page; in order to help a reader keep her
place, the most recently looked at part of the screen
is highlighted.
The important thing about the Stanford research, says
Shumin Zhai
, researcher at IBM Almaden Research Center in San
Jose, CA and pioneer in the eye-tracking field, is
that Kumar "has been working on making eye tracking
practical for everyday tasks." However, Zhai says that
there may still be a barrier for the average person
because she needs to go through a calibration
process in which the software measures how quickly her
eyes move.
There are some signs that eye-tracking technology
could find its way to the consumer market soon.
Apple's desktops and laptops are now equipped with a
built-in
camera for videoconferencing. If a higher-resolution
camera, infrared LEDs, and software were added,
Apple's machines would be able to support applications
from the GUIDe project, says Kumar. If eye tracking
proves appealing to the consumer, and the hardware
costs drop to a reasonable range, eye-tracking
interfaces
could provide an alluring and entertaining alternative
to the mouse or laptop track pad. "It's almost like
magic when it's working," says Tufts's Jacob.
"The sensation you get is that the computer's reading
your mind, and that's really very powerful."
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