New device brings virtual vision
to the blind
A NEW Swedish computer interface device makes it possible for a
blind person to touch virtual objects, much like a sighted person
can see objects or pictures on a computer screen.
using Phantom: A six-year-old girl uses the Phantom device.
Pot: FreeForm modelling system allows users to model products
in a digital 3-D environment
apparatus, called the Phantom (SensAble Technologies, US), investigated
by a Swedish research team, is a haptic interface which transmits
forces to the user’s hand or fingers in a way that mimics
the sensation of touching real objects, Charlotte Magnusson PhD
told the 7th International Conference on Low Vision.
She noted that ‘haptic’ in this sense refers to the
perception and manipulation of objects using the sense of touch.
The device’s users either hold a pen-like object or place
their fingertips into thimble-like cups. When the user moves the
pen or the thimble against a virtual object, the device transmits
resistance to their hand or fingers, she explained.
In the study involving 25 blind individuals aged between 12 and
85 years, only the oldest subjects had difficulty using the apparatus,
and most quickly acquired competence in identifying mathematical
curves, describing virtual objects and finding their way around
a virtual reality modelling language (VRML) environment.
All received training in the use of the device and practised before
participating in the test.
The testers were able to observe the test subjects’ manipulation
of virtual objects and navigation in virtual environments on a computer
All subjects performed successfully the task of finding, examining
and identifying abstract 3-D geometrical objects in tests, but they
tended to have difficulty distinguishing cubic objects from rectangular
A task involving the recognition of three such objects in a grid
turned out to be more problematic, and although most users got the
locations and the number of objects right only nine users managed
to get everything right.
When asked to identify and describe more realistic types of objects
such as a vase, a grand piano and a stool, most subjects performed
Among four who were presented with a virtual guitar and sword, three
could identify the guitar and all could describe the different parts
of the sword, although none of them could identify it as a sword
because it was not sharp.
“This shows that the key visual elements and the ones you
touch are not necessarily the same, so you have to be quite careful
when designing these virtual models. The blind users are not greatly
disturbed by the VRML approximation, but poorly modelled parts make
it difficult to understand the virtual objects,” Dr Magnuson
Another test involved a series of mathematical surfaces. All of
the seven subjects who did this test could understand, describe
and discuss the mathematical surfaces. This test only involved users
that had a special interest in mathematics.
The final test involved a haptic VRML environment consisting of
six houses with moving blocks representing cars on the roads. These
‘cars’ could hit the subject, and when this happened
the sensation of being hit was this accompanied by a loud and annoying
screech. Most subjects found it easy to navigate between the houses,
and users who were ‘hit’ by a moving box (a ‘car’)
said they found it very realistic.
“Apparently this was a pretty effective environment. First
of all, they enjoyed it and they also found it fairly realistic.
This is an example of an environment that illustrates the importance
of context, as it would be quite confusing if the users had not
known that it represented a traffic environment,” Dr Magnusson
She noted that the test results indicated that the subjects sometimes
appeared to find complex but realistic environments easier to navigate
than more simple but abstract ones.
Similarly, the subjects in some cases appeared to find geometrical
objects more difficult to identify and describe than more realistic
models. She stressed that these results must be subject to further
testing because the tests in the present series involving abstract
or realistic objects were not strictly comparable.
“For those of us who are working with these kinds of people,
the results are very encouraging. Our research shows that context
is important to help the user get the right understanding of a more
complex environment. It’s also very useful to add sound or
other types of input,” Dr Magnusson stressed.
Lund University, Sweden