A
doorknob that knows whether to lock or unlock based on how it is
grasped, a smartphone that silences itself if the user holds a finger to
her lips and a chair that adjusts room lighting based on recognizing if
a user is reclining or leaning forward are among the many possible
applications of Touché, a new sensing technique developed by a team at
Disney Research, Pittsburgh, and Carnegie Mellon University.
Touché
is a form of capacitive touch sensing, the same principle underlying
the types of touchscreens used in most smartphones. But instead of
sensing electrical signals at a single frequency, like the typical
touchscreen, Touché monitors capacitive signals across a broad range of
frequencies.
This
Swept Frequency Capacitive Sensing (SFCS) makes it possible to not only
detect a “touch event,” but to recognize complex configurations of the
hand or body that is doing the touching. An object thus could sense how
it is being touched, or might sense the body configuration of the person
doing the touching.
SFCS
is robust and can enhance everyday objects by using just a single
sensing electrode. Sometimes, as in the case of a doorknob or other
conductive objects, the object itself can serve as a sensor and no
modifications are required. Even the human body or a body of water can
be a sensor.
“Signal
frequency sweeps have been used for decades in wireless communication,
but as far as we know, nobody previously has attempted to apply this
technique to touch interaction,” said Ivan Poupyrev, senior research
scientist at Disney Research, Pittsburgh. “Yet, in our laboratory
experiments, we were able to enhance a broad variety of objects with
high-fidelity touch sensitivity. When combined with gesture recognition
techniques, Touché demonstrated recognition rates approaching 100
percent. That suggests it could immediately be used to create new and
exciting ways for people to interact with objects and the world at
large.”
In
addition to Poupyrev, the research team included Chris Harrison, a
Ph.D. student in Carnegie Mellon’s Human-Computer Interaction Institute,
and Munehiko Sato, a Disney intern and a Ph.D. student in engineering
at the University of Tokyo. The researchers will present their findings
May 7 at CHI 2012, the Conference on Human Factors in Computing Systems,
in Austin, Texas, where it has been recognized with a prestigious Best
Paper Award.
Both
Touché and smartphone touchscreens are based on the phenomenon known as
capacitive coupling. In a capacitive touchscreen, the surface is coated
with a transparent conductor that carries an electrical signal. That
signal is altered when a person’s finger touches it, providing an
alternative path for the electrical charge. By monitoring the change in
the signal, the device can determine if a touch occurs.
By
monitoring a range of signal frequencies, however, Touché can derive
much more information. Different body tissues have different capacitive
properties, so monitoring a range of frequencies can detect a number of
different paths that the electrical charge takes through the body.
Making
sense of all of that SFCS information, however, requires analyzing
hundreds of data points. As microprocessors have become steadily faster
and less expensive, it now is feasible to use SFCS in touch interfaces,
the researchers said.
“Devices
keep getting smaller and increasingly are embedded throughout the
environment, which has made it necessary for us to find ways to control
or interact with them, and that is where Touché could really shine,”
Harrison said.
Sato
said Touché could make computer interfaces as invisible to users as the
embedded computers themselves. “This might enable us to one day do away
with keyboards, mice and perhaps even conventional touchscreens for
many applications,” he said.
Among
the proof-of-concept applications the researchers have investigated is a
smart doorknob. Depending on whether the knob was grasped, touched with
one finger or two, or pinched, a door could be programmed to lock or
unlock itself, admit a guest, or even leave a reply message, such as
“I’ll be back in five minutes.”
In
another proof-of-concept experiment, they showed that SFCS could
enhance a traditional touchscreen by sensing not just the fingertip, but
the configuration of the rest of the hand. They created the equivalent
of a mouse “right click,” zoom in/out and copy/paste functions depending
on whether the user pinched the phone’s screen and back with one finger
or two, or used a thumb.
The
researchers also were able to monitor body gestures, such as touching
fingers, grasping hands and covering ears by having subjects wear
electrodes similar to wristwatches on both arms. Such gestures could be
used to control a smartphone or other device.
They
also showed that a single electrode attached to any water vessel could
detect a number of gestures, such as fingertip submerged, hand submerged
and hand on bottom. Sensing touch in liquids might be particularly
suited to toys, games and food appliances.
Source: Carnegie Mellon University
