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DESIGNING HAPTIC COMPUTER INTERFACES FOR BLIND PEOPLE 
Calle Sjöström
Certec, Lund University
Box 118
S-221 00 Lund, Sweden
+46-46-222 40 38
www.certec.lth.se/haptics
[email protected]
ABSTRACT
Certec has been working on touch interfaces – haptic
interfaces – since 1995, exploring the possibilities they can
offer people with different kinds of disabilities. With a
haptic computer interface a blind person can learn
mathematics by tracing touchable mathematical curves,
playing haptic computer games, and gaining better access
to graphical user interfaces like Windows.
This paper presents a brief overview of a set of tests that
have been made and some of the results from these tests.
This is followed by a set of design recommendations that
we have been able to extract as an extended result of this
research and development work. These guidelines are
grouped under the headings Navigation, Finding objects,
Understanding objects, Haptic widgets and Physical
interaction.
1 INTRODUCTION
Computer access and the wide adoption of the Internet as
an information channel have given blind persons access to
information that used to be almost inaccessible. The fact
that text in digital form can be easily accessed has actually
given blind persons a new way of communicating with the
rest of the world.
Most blind computer users have a screen reader combined
with synthetic speech and/or a Braille display. This gives
them access to text on the screen, but not to the graphics.
Haptic interfaces use the sense of touch in user interaction.
With a haptic interface it is thus possible to feel shapes
that are based on digital information. There are now
computer programs available that present some of the
graphical information in a GUI via a haptic device.
Certec is the Division of Rehabilitation Engineering
Research, Department of Design Sciences, Lund Institute
of Technology at Lund University in Sweden. We have
been working with haptic computer interfaces and haptic
games for blind people since 1995.
2 THE EXPERIMENTS
This paper presents a set of principles for haptic user
interface design. The user tests and experiments that lay
the foundation for this article have not been designed
specifically to achieve or test the principles. Instead, these
tests have been conducted to test different user interface
ideas, games etc. and to get an idea of how useful it can be
to include haptics in a computer interface for blind people.
The principles have emerged and been refined with “reflection-
in-action” and “reflection-on-action” [4] during
our tests and software development. We have found these
recommendations useful, and we believe that they can
work as general guidelines for all developers of haptic
interfaces for blind people.
2.1 User tests of a haptic memory game -
The Memory House
These tests were conducted to find out if it is possible to
understand and control a system like Windows with only
haptic and auditive information.
The game consists of 25 buttons that produce a sound
when pressed. There are 12 sound pairs and one nonpaired
sound (the “Old Maid”). The buttons disappear
when the player presses two buttons with the same sound
in sequence.
Figure 1. The Memory House
In the Memory House, the buttons are placed on five
different floors. Between each row of buttons the user can
feel a thin barrier that helps him to stay within one set of
buttons. To make navigation among the floors easier, there
is a voice that reads the number of the floor each time the
user moves from one floor to another.
The program has been tested in a study comparing sighted
and blind people (nine blind persons of different ages and
23 sighted children). The sighted testers used a regular
mouse and pictures or sounds, while the blind testers used
the PHANToM and sounds.
The main results from these tests indicate that it is possible
for almost any blind user to navigate among the sounds
and buttons in the game. Of the nine blind persons in our
initial test only two were unable to finish the game
(although they managed to find a few pairs). The other
seven users managed to find all the pairs and many of
them finished the game using about as many button pushes
as the sighted testers. However, most of the blind testers
needed more time than their seeing counterparts [6][7].
2.2 Pilot studies with Immersion’s FEELit Mouse
In these tests, we conducted three different experiments
using a prototype of the FEELit Mouse from Immersion
Corporation. The experiments where:
1. Combining FEELit Desktop with synthetic speech for
general Windows access
2. Testing “radial haptic menus”
3. Testing a set of virtual haptic search tools that can be
used as aids in finding scattered virtual objects such as
icons on the desktop.
The first is an example of direct translation from graphics
to haptics. FEELit Desktop from Immersion is a program
that directly translates many graphical interface objects to
corresponding haptic objects. Our work has been to try to
determine how well FEELit Desktop can compensate for
things that are not made accessible by the speech
synthesizer.
Radial menus are menus where the choices are indicated
as rays pointing out from a center instead of being
arranged in a column as in ordinary linear menus. A radial
menu can be likened to a pie or a clock. In this case a
radial menu with 12 choices was used and that made it
very easy to use a clock analogy (e.g. “Copy is at three
o’clock”).
The virtual search tools are intended to help the user when
exploring an unknown environment, for example, the
Windows desktop on somebody else’s computer. With
these tools it is possible to feel objects without touching
them directly. Three different search tools were proposed
but only the first one was tested in this experiment.
 A “cross” that makes it possible to feel when you line
up with an object horizontally or vertically.
 A “magnet” that pulls the user towards the nearest
object.
 A “ball” that makes it possible to feel objects at a
distance but with less detail.
We have carried out a case study of the usability and
usefulness of these concepts involving two blind computer
users [8]. Both users had minor problems with the small
workspace of the FEELit Mouse. Their spontaneous
reaction was: “This device requires tiny, tiny movements.
Can’t it be made a little bit bigger?”
The radial menus worked very well for both of the testers.
They were successful in handling the menus and they were
also able to make good use of the clock metaphor. Even
though both testers thought that these menus worked well
they where skeptical about introducing them in a Windows
access system. They both wanted the access system to be
as transparent as possible and they wanted it to give them
the same picture as a sighted person gets when looking at
the monitor.
The cross search tool was especially well accepted by one
of the testers. He found the cross very helpful when
searching. The other user was more uncertain about the
cross. He talked more about magnetic objects as a way to
guide the user. Since all search tools apart from helping
the user to find and explore virtual objects, also alter the
sensation in different ways, it seems important to be able
to easily switch between different search tools and no tool
at all.
2.3 Informal demos and tests of a haptic games and
programs
Certec has developed a number of haptic games and
programs that have not been tested formally. However the
programs have been demonstrated at exhibitions and
conferences to both sighted and blind visitors, and there
also have been many trial sessions at Certec with blind
children and adults, as well as with a group of deaf-blind
persons.
The programs used at these sessions were scenes with
simple static or dynamic geometrical objects, a game
called “Submarines”, and a simple clay-modeling program
(provided by SensAble Technologies).
“Submarines” is a haptic variant of the well-known battleship
game. The ordinary pen-and-paper-based battleship
game has been used to give school children an initial idea
of what coordinate systems can be used for. With
“submarines” it is possible for a blind child to get the same
kind of playful introduction to coordinate systems.
The player feels 10x10 squares in a coordinate system. In
the game, your finger in the PHANToM is a helicopter
that is hunting submarines with depth charge bombs. If
you put your finger on the “surface of the water” you can
feel smooth waves moving up and down. There are four
different states for a square with associated haptic
feedback:
 Not yet bombed - calm waves
 Bombed, but missed - no waves (flat)
 Bombed, hit part of a submarine - vibrations
 Bombed, hit entire submarine - bubbles
“Submarines” has also been tried by a group of deaf-blind
persons. Since the different conditions of the squares are
provided as haptic feedback, our hypothesis was that it
should work well for deaf-blind users too. As it turned out,
it seemed like the haptic feedback of the game was
sufficient, in all but one case. In the game, the space key is
used to drop the bomb in the water, and while the bomb
falls, a hearing person hears the sound of the falling bomb
in the speakers. However the deaf-blind users became
confused since they did not get any haptic feedback before
the bomb reached the water and there was no direct haptic
feedback indicating whether it was a hit or not.
The first PHANToM program at Certec was a painting
program for blind children, “Paint with Your Fingers”.
With the PHANToM, the user chooses a color from a
palette. Each color on the palette has an associated texture
that the user feels when painting with it. By changing
program mode the user can feel the whole painting and
also feel what other people have painted.
All of these programs have been tested by more than 20
blind children [5][7]. Perhaps the most interesting result
from these sessions was that it is actually possible for a
blind person to use virtual touch to create an inner picture
of rather complex environments. And they are also able to
connect sounds to objects in this inner picture.
Another finding is that some of the subjects were able to
compare what they felt with the PHANToM to earlier
experiences. For example, one tester likened a virtual
model of a house to “The money box I got from the bank
when I was a child”. The money box he mentioned had the
form of a small house and he remembered it from the time
when he could still see.
2.4 A haptic mathemathics program
Early in our work we also developed a simple mathematics
program. People who try to explain mathematics to blind
persons often notice that to some extent it is a visual
subject. Our program makes it possible to feel a
mathematical curve or surface with the PHANToM. A
program like this can help blind persons to understand
equations in terms of curves and surfaces. A similar
program, but with more functionality, has been developed
at ASEL, University of Delaware [1].
It is interesting to compare the two programs because they
demonstrate two different ways of showing 2D graphs in a
3D environment. The program from ASEL displays the
graph as a thin line with a “virtual fixture”, which gives
the line an attractive force that helps the user find and
follow the function. The program from Certec shows the
function as a ridge or a groove in a flat surface. In this
case the user can sweep the surface until she finds the
ridge or groove and then follow it easily. Both ways are
feasible.
3 APPARATUS
Most of our work has been carried out with the
PHANToM, a high performance, 3D haptic interface from
SensAble Technologies. We have also used other devices
such as force feedback joysticks and the FEELit Mouse
from Immersion Corp.
Figure 2. The PHANToM (photo by SensAble Technologies
Inc.)
4 GUIDELINES FOR POINT
INTERACTION HAPTICS -
DESIGN REQUIREMENTS
In the course of the work with the above-mentioned
experiments we have also gained general knowledge and
experience of using haptics in computer interfaces for
blind people. This knowledge was first summarized in my
licentiate thesis “The IT Potentials of Haptics – Touch
Access for People with Disabilities” [8]. The list presented
here is a revised version of those principles.
4.1 Navigation
 Provide well defined and easy-to-find reference points
in the environment. This is necessary to facilitate
navigation. Natural reference points are for example
the corners of a room. Good reference points are easy
to find and come back to, and they should also be easy
to identify [6].
 Do not change the reference system unnecessarily. A
disabled haptic button should not be removed, but
rather “grayed out” for example by giving it a different
texture and making it impossible to click. This way the
button can still be used as a reference point even
though it is nonfunctional. [6].
4.2 Finding objects and getting an “overview”
 With pure one-point haptics it is easy to miss an object
even if one is really close to it. One can often
compensate for this when designing haptic software by
using objects with large connected surfaces rather than
scattered, thin and/or small objects [6][8].
 It can be just as difficult to determine that an object
does not exist as it is to find an object. It is always
easier to move along some kind of path (a ridge, a
groove, a magnetic line, etc.) to the place where the
object is located or where there is no object [6][8].
 In both of the cases just mentioned one can also choose
to give the user a “virtual search tool” [8] instead of
changing the virtual objects. A virtual search tool
could be a bar, a ball, or a magnet, for example.
4.3 Understanding objects
 If it is not absolutely necessary for the haptics to feel
like something real, it may be beneficial (and
sometimes essential) to help the user follow the outline
of the object. It is easy to make a thin touchable hose
easier to find by giving it the appropriate attractive
force. Without such a force it is almost impossible to
feel the hose in 3D [1].
 Sharp edges and corners are much more difficult to
feel and understand than rounded shapes when they are
felt from the “outside”. The user almost always loses
contact with the object when moving past a sharp
corner, thereby disturbing the cognitive process that
translates the impressions received into an inner
picture. Moreover, it is difficult to determine the size
of the angle; many users believe that the angle is more
acute than it really is [6].
4.4 Haptic widgets
 When going through a thin wall or past an edge, the
finger often accelerates a great deal. Consequently, the
next wall or edge should not be very close since there
is a risk that the finger will go through that wall as well
(sometimes without the user noticing). In this case it
can sometimes help to replace the thin walls (between
the areas) with a magnetic line that pulls the user to the
center of the area instead. The problem becomes
apparent when one wishes to represent menus and
coordinate systems [3][8].
4.5 The physical interaction
 Be careful with the manipulandum design. The
manipulandum is the tool that the user grasps in his
hand. In the PHANToM the manipulandum is a stylus
or a thimble. In other cases it might be a mouse body, a
joystick handle or some specialized tool. The choice of
manipulandum can affect the haptic sensation a great
deal. This is because the form and surface of the
manipulandum have an effect on how the resistive
force is applied to the user, the kind of movements
used, and the feeling of being in contact with the
virtual object. For example, a thimble with sandpaper
on the inside causes many people to use less force
when grabbing a virtual object because they get the
sensation that the objects are less slippery [2][8].
5 CONCLUSION
Haptic interfaces can be used in many different kinds of
computer programs for blind people. We have found that
our haptic programs in general work better when
considering these guidelines, even though we do not claim
to have complete knowledge of how digital objects should
be accessed haptically in all cases.
Some of the tests presented here make effective use of
sounds along with the haptic information; we have found
that sound and haptics often complement each other very
well.
We will continue our work with haptic interfaces and
expect to refine and add to this list of guidelines
continuously.
6 REFERENCES
[1] Fritz, J. P., Barner, K. E. Design of a Haptic
Visualization System for People with Visual
Impairments, IEEE Transactions on Rehabilitation
Engineering, vol. 7, No 3, 1999, pp 372-384.
[2] von der Heyde, M. Psychophysical experiments in a
complex virtual environment, Proc. of the Third
PHANToM User Group Workshop, Dedham, MA,
USA, 1998.
[3] Miller, T., Zeleznik, R. An insidious haptic invasion:
Adding Force Feedback to the X desktop, Proc. of the
Third PHANToM User Group Workshop, Dedham,
MA, 1998.
[4] Schön, D. The Reflective Practitioner, Basic Books,
1983.
[5] Sjöström, C. Jönsson, B. To Use the Sense of Touch
to Control a Computer and the World Around You.
Proc. of the AAATE conference, Thessalonica,
Greece, 1997.
[6] Sjöström, C. The Phantasticon - Haptic Interfaces
Give New Possibilities for Blind People. Master’s
Thesis, Certec, Lund University, Sweden, 1997.
[7] Sjöström, C., Rassmus-Gröhn, K. The sense of touch
provides new interaction techniques for disabled
people, Technology & Disability Volume 10, Number
1, IOS Press, 1999.
[8] Sjöström, C. The IT Potential of Haptics – Touch
Access for People with Disabilities, Licentiate Thesis
Certec, Lund University, Sweden, 1999.

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