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OCR for page 67
Chapter 6
THE TECHNOLOGY OF ELECTRONIC TRAVEL AIDS
On the basis of some assumptions regarding the types of
environmental information needed to enhance independent travel by
visually impaired people, this chapter provides a review of mobility
aid technology to date. We discuss strengths and weaknesses in the
information acquisition and display of these devices, and we make
suggestions for research aimed at improving on past aids, along with
speculation regarding existing and future technology that could be
applied to the problem.
INFORMATION NEEDS OF THE: PEDESTRIAN
As previous chapters have discussed, it is generally accepted that,
in order to engage in safe and efficient travel, the pedestrian must
have access to certain categories of environmental information. Sug-
gestions regarding the information needed have been put forward by
Foulke (1971), Kay {1974), Strelow (1985), and others and usually
include the following concepts:
(1) Information is needed regarding the presence, location, and
preferably the nature of obstacles immediately ahead of the traveler,
from ground level to head height and over a wide enough area hori-
zonta]ly to cover the width of the traveler's body. The minimum
distance or range over which this information is needed is a com-
fortable stopping distance at normal walking speed. A greater range is
desirable.
(2) Information regarding the path or surface on which the traveler
is walking is highly desirable; this includes texture, gradient, and
upcoming steps (both up and down) and boundaries to left and right
(including step-downs at sidewalk edges).
(3) Information regarding the position and nature of objects to
the sides of the travel path is desirable. This includes hedges,
fences, doorways, trees, etc., forming part of the shoreline on either
side of the path.
(4) Other information to enable the traveler to maintain a straight
course is extremely helpful, notably the presence of some type of aiming
point in the distance, often provided in practice by distant traffic
67
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sounds. Knowledge of absolute or relative direction of travel is also
helpful.
(5) Information on landmark location and identification is
needed. This can include information under the above categories
(especially 3) and also includes the ability to positively identify
specific environmental features such as building entrances, room
numbers, elevators, rest rooms, floor numbers, intersections, etc.
(6) Sufficient information must be provided by one means or
another to allow the traveler to build up a mental map, image, or
schema for the chosen route to be followed, including turns and other
discontinuities.
PAST AND PRESENT MOBILITY AIDS
With the above assumptions in mind, we examine the progress to date
in technology designed to acquire and display at least some of the
above types of information.
The Long Cane
The long cane, introduced in its present form by Richard Hoover
(1950) in the late 1940s, effectively allows detection of obstacles
within a 3-foot range and tends to warn other pedestrians to get out of
the way. The former feature requires fast stopping reaction or slower
walking speed when an obstacle is encountered, while the latter does
not add to the grace of independent travel. The skilled user of a cane
can, however, acquire directly most of the information needed regarding
obstacles and path or surface. In addition, location cues from the
sounds emitted when the cane tip (especially a metallic tip) contacts
the ground can provide a surprising amount of the additional information
regarding objects at the sides of the path. These subtle cues are
frequently unknown to, or underrated by, the sighted community (except
for mobility specialists) and their presence provides a powerful
incentive for skilled blind pedestrians to eschew electronic travel
aids. These subtle cues and their use receive a great deal of
attention in orientation and mobility training.
Electronic Travel Aids
Following the development of radar and sonar technologies for
remote sensing during World War II and the introduction of transistor
technology, which made portable electronic devices practical, inventors
began to see the potential for various obstacle-detection devices to
aid blind people. A huge number of such devices were developed, mostly
using the transmission of an energy wave (usually ultrasonic) and the
reception of echoes from objects in or near the traveler's path. The
choice of ultrasound for the transmission medium, as opposed to light
or radio waves, was dictated by the convenience with which echo ranging
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69
could be performed in this medium due to the relatively slow speed of
propagation. Optical sensing was used in some cases, when the operation
of the system was passive or when range measurement was not a design
goal (e.g. in the Laser Cane).
Sonar technology, as it existed by 1960, was well developed for
underwater purposes, but its use above water was complicated by much-
increased signal attenuation and the difficulty of coupling a transducer
effectively to the air. These problems were overcome, and ultrasound
became the most popular sensing medium for mobility aids. The main
limitations of the technology were limited useful range and difficulties
experienced with reflections from smooth surfaces (which act like
mirrors to ultrasound due to its long wavelength).
Clear-Path Indicators Versus Environmental Sensors
Once the technical problems had been solved, the principal arguments
among developers revolved around the amount and type of information
that is desirable to present to the user and the manner in which it
should be presented. Development followed two schools of thought. One
class of aids, known as obstacle detectors or clear-path indicators
(Foulke, 1971), warned only of the presence and sometimes the approxi-
mate range of obstacles directly in the travel path, while generally
not being concerned with identification of the obstacles detected.
Such devices generally had the advantage of relatively lower cost.
Included in this category is the Russell Pathsounder (Russell 1965~,
which uses a 30-degree ultrasonic beam transmitted from a chest-level
unit suspended from the user's neck. It can provide tactile and
auditory warning of objects up to 6 feet ahead and allows some range
estimation. The Mowat Sensor (Presley 1977) is a hand-held, pulsed
sonar system with tactile output. The narrow-beam, flashlight-sized
device vibrates with a period proportional to target range. The
Nottingham Obstacle Detector (Armstrong 1973) is similar in operation
and shape to the Mowat Sensor, except that it provides an auditory
readout of range with eight notes corresponding to the musical scale.
The Laser Cane (Nye, 1973) is a conventionally shaped long cane with
laser emitters and receivers aimed to detect overhangs, down curbs, and
targets straight ahead within a selectable range of 6 to 12 feet,
giving auditory and tactile warnings.
A second category of aids, known as environmental sensors (Foulke,
1971) attempts more than mere detection of obstacles. The first of
these to be developed--and one of the most well known--is the Kay Sonic
Torch (Ray 19641. One of the few devices designed to replace rather
than merely supplement the long cane or dog guide, the Sonic Torch
{which is no longer in production) was a hand-held, narrow-beam
ultrasonic device with an auditory output presented via an earphone.
The Sonic Torch, in contrast to those ultrasonic travel aids of the
obstacle-detector class (which normally use simple single-frequency
pulse transmission), transmitted a wide-bandwidth (40-80 kHz),
frequency-modulated, ultrasonic energy wave. Reflected signals from
the Sonic Torch were converted to the audible region by multiplication
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with the transmitted signal. The result was an auditory signal
extremely rich In information--the pitch corresponding to range and the
timbre corresponding to variations in target surface texture, enabling
target identification.
Later developments in this concept led to the Binaural Sensory Aid
(Kay 1966), known commercially as the Sonicguide. Employing the same
methods of transmission and reception as the Sonic Torch, this device
looks like a pair of spectacle frames; it is worn on the head with a
wide-beam (60-90 degree) transmitter. The two receiving transducers
are splayed a few degrees to the left and right, and their signals are
presented separately to the left and right ears, giving a built-in
direction cue. The Sonicguide is used in conjunction with the long
cane or dog guide, like most other electronic mobility aids.
Recent Developments
The first generation of mobility aids, described above, was
criticized on grounds that included cost-effectiveness, the masking of
natural echo-location cues, and the necessity of training for the more
complex aids.
In the late 1970s and early 1980s, device developers came up with
some new solutions and refinements to address these problems. Criticism
of the degree of information presented by the Kay Binaural Sensory Aid
was answered by the development of a prototype single-channel system
with a narrow beam width, eliminating the constant signals returned by
objects in the periphery, while retaining the advantages of the binaural
version for object identification.
To shed light on the controversy regarding the optimal form of range
cue for an obstacle detector, the American Foundation for the Blind
developed a microprocessor-assisted ultrasonic ranging device (Maure et
al., 1979) using the sonar electronics from the Polaroid auto-focusing
mechanism. The microprocessor can be programmed to present its output
in any one of a variety of auditory codes, including the spoken voice.
Other Polaroid-based ranging systems have also been developed (Heyes,
1982~. In the Federal Republic of Germany, the Siemens Company produced
its own spectacle-worn and hand-held obstacle-detector systems, while
in England the developers of the Nottingham Obstacle Detector devised a
modified head-worn version, the Sonic Pathfinder {Heyes, 1984), designed
to allow discrimination of target direction while remaining basically
an obstacle-detection system.
Investigations were made of the feasibility of tactile information
presentation in a mobility aid, in order to overcome the criticized
masking effects of auditory displays {and also for use by people who
are both deaf and blind). Early research in this field at Smith-
Kettlewell and elsewhere (Collins, 1967; Collins and Madey, 1974),
centered on the direct presentation of television camera images on the
skin, on a point-for-point basis using large (32 x 32 or 20 x 20 point)
tactile arrays on the abdomen. As discussed in Chapter 5, it was
concluded that this concept has educational value when confined to
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simple images and shapes, but the complex scenes encountered outdoors
cannot be readily interpreted through the skin for use in travel.
Two alternative approaches were then investigated for preprocessing
the tactile information, thus simplifying the display. The first
approach used a scanning sonar system (Brabyn et al., 1981) to present
a plan-type view of the environment on the skin, displaying range and
azimuth information in the same manner as a PPI radar display. This
approach was successfully tested, but the expense of the large tactile
arrays militated against successful commercialization. An alternative
approach, using computer processing of video images to extract only the
features vital to mobility (such as curbs, poles, fences, etc.), was
then tested. Range and direction were coded on a one-dimensional
tactile array, and supplemental synthetic speech information was used
in the system output {Collins and Deering, 19841.
In order to overcome difficulties experienced with ultrasonic
obstacle sensors when attempting to detect smooth surfaces at oblique
angles, an infrared ranging system was designed at Smith-Kettlewell.
The prototype device uses a disparity technique that does not require
complex electronics for propagation delay measurements. The initial
version uses an auditory output, with an inverse relationship between
pitch and range. The beam is extremely narrow (approximately 5
degrees), and smooth surfaces such as linoleum can be detected at
angles up to approximately 60 degrees from the perpendicular.
Orientation Aids
Orientation involves two aspects: (1) area familiarization--becoming
acquainted with a geographical area or with routes within it and (2)
navigation--finding one's way from location A to location B. Navigation
can be accomplished either by keeping track of one's position with
respect to prominent landmarks or by following a series of rote
directions.
The primary aids used in area familiarization in the past have been
the use of a sighted guide or a factual map. Experience and research
have shown factual maps have met with only limited success in familiar-
izing blind people with a complex environment, such as a city or
college campus. Several electronic aids have recently been developed
to assist in both area familiarization and navigation. The "Talking
Signs" system (Loughborough, 1979), developed at Smith-Kettlewell, uses
a network of low-cost infrared transmitter modules placed on normal
navigational signs in the environment, such as street corners, bus
stops, corridors, and room and building numbers. A voice output
corresponding to the wording of the sign is produced by a a hand-held
receiver, which receives the infrared transmissions and converts them
into a spoken message. Each transmitter contains a computer memory
chip on which its message is stored. This system is now in commercial
production.
A similar idea is being pursued by the Georgia Institute of
Technology in the development of its Sonic Orientation Navigation Aid
(SONA) system (Kelly, 1981~. This orientation aid uses radio-activated
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auditory beacons to accomplish the task. If, for example, a user is
searching for an elevator, he or she enters a corresponding numerical
code on a key pad mounted on the hand-carried transmitter. The trans-
mitter then interrogates any receivers in the vicinity. If a receiver
is present on an elevator nearby, it will accept the code and produce
an auditory beep.
Obviously, successful dissemination of such orientation and
navigation systems is problematic, due to installation costs. Even
though substantial and expensive modifications to the environment have
been made for the benefit of wheelchair users, it does not currently
appear likely that the same types of changes will be made for the blind
population.
Optical Aids for Low Vision
While low vision encompasses a wide range of visual impairment,
existing optical orientation and mobility aids may nevertheless be
divided into four types: distance magnifiers, minifiers, absorptive
filters, and image intensifiers. In many cases an aid is designed to
serve more general purposes for the individual than orientation or
mobility.
Distance magnifiers (telescopes) (Bailey, 1984) are used for the
identification of environmental features such as signs, room numbers,
etc., and in orientation to identify hedges, fences, doorways, trees,
etc. Considerable skill is required in the use of these aids for the
following reasons.
First, the optical leverage of a telescope amplifies small hand
tremors into large image translations, making their use suitable only
for those with a steady hand (which older people are less likely to
have). Second, because the image through a telescope portrays only a
small area of the environmental field, it is difficult to aim the
device at a desired object. To read a street sign, for example, the
user may have to track along the length of the sign pole as an aid to
sighting. Third, focusable telescopes are difficult and inefficient
use, especially when the image of best focus is degraded by the very
optical and neural impairments that bring about the need for a
telescope.
Additional limitations of telescopes are that: (1) considerable
light loss lowers the image luminance, reducing visibility of details
and overall effective contrast and (2) for fixed focus (to infinity)
telescopes, minimum usable range is restricted to greater than 6 meters.
A second class of optical aids for low vision includes image
minifiers' such as reversed telescopes. While distance magnifiers
expand a small portion of the field to a size that allows identification
for those with central field and/or resolution losses, minification
aids compress a wide field to a small central region of the retina.
They are designed to allow detection and identification of objects on
the periphery of the travel path for individuals with field constric-
tions. Minification aids suffer from the same light loss problems as
forward telescopes and have not been well accepted in practice. Users
to
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also find the unnatural optical flow pattern disturbing. The user is
inadvertently retraining the vestibular-ocular response with these aids
and may find that they produce dizziness and even nausea.
A variant of this technique is the Amorphic Lens by Designs for
Vision, which compresses the field only along the horizontal dimension,
presumably on the theory that the view along the sides of the observer
is more important for mobility than that in the vertical periphery.
The Amorphic Lens produces somewhat disturbing distortions of the
field, as the relative sizes of objects change with continuous rotation
of the head, but it is considerably more graceful to use than
spectacle-mounted or hand-held magnifiers or minifiers.
A third class of aids is the absorptive lenses. It includes
sunglass and Polaroid filters, which reduce ordinary glare from
sunlight and specular reflections, and filters that selectively absorb
light from one part of the visible and/or invisible spectrum. Selective
filter are used primarily to remove short wavelength light that scatters
more easily than long wavelength light and to remove ultraviolet light
that with some pathologies can produce fluorescence of the media. Light
scatter and fluorescence, of course, degrade the retinal image and
reduce overall contrast, and such filters are designed to alleviate
such effects. An important trade-off, however, is the problem that
reducing the light with filters also reduces effective contrast of the
image.
The fourth class of mobility aids for low vision is the image
intensifiers, intended especially for those with retinitis pigmentosa.
These range from simple devices, such as wide-angle lamps {Morrisette
and Goodrich, 1983), which increase illumination and hence effective
contrast on and around the travel path, to more sophisticated devices,
like the ITT Nightscope (Berson et al., 19731, which displays a video
image of the system travel path sensed by a photo multiplier that is
more sensitive than the eye. These aids suffer from a lack of grace
and are effective only to the extent that the user can see and
interpret the information acquired visually.
LIMITATIONS OF EXISTING TECHNOLOGY
As stated at the outset of this report, the functional utility and
user acceptance of mobility aids should be considered in the context of
the four criteria for successful mobility: safety, comfort, grace, and
independence. None of the aids produced to date has achieved broad
market penetration. In part this has been due to the resistance of
some groups of consumers to use or support the use of electronic
mobility aids, and in part to the limitations of the technology
itself. There are a number of probable reasons for this phenomenon:
· Information Limitations. It is evident that each of the
approaches taken to date by designers of mobility aids is capable of
acquisition and display of only a subset of the required mobility
information outlined earlier. No device by itself--including optical
aids or the long cane--provides all the required or desired information.
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· Expense. All commercially available electronic travel aids
are relatively expensive, costing between $300 and $3,000.
· Relation to the Long Cane. Most are designed to supplement
(rather than replace) the long cane or dog guide, and there is
disagreement over whether the additional information they provide is
worth the very considerable extra cost and the effort of training. A
skilled user of the long cane can use the sounds emitted by the
metallic cane tip for natural echo-location, providing a surprising
amount of information about the immediate environment. This category
of user, although not typical of the general population, would require
substantial additional input from an electronic aid for its use to
become worthwhile.
· Auditory Cues. The auditory displays of many aids may mask
the subtle echo-location cues mentioned above as well as important
ambient sounds.
· Training Difficulties. For the more complex aids, the
training required to master their use generates resistance. This
appears to apply to many optical aids as well as electronic ones.
· Conspicuousness. Most aids to date for both blind and
partially sighted people are conspicuous (not meeting the criterion of
grace), and many are not conveniently removed or deactivated when not
needed.
· Limitations of Scale. Those aids developed to date addressing
orientation problems would be very expensive to install on a large
scale.
· Lack of Performance Measures. There has been little success
in demonstrating that optical or electronic aids for blind and partially
sighted people actually improve their mobility. This lack of success
reflects the crudeness of measures as well as the limitations of the
aids themselves.
Although these speculations are offered the reasons for the lack of
acceptance of optical and electronic aids for mobility, not all the
reasons are well understood--particularly in the area of magnifiers and
minifiers for partially sighted people. In summary, the market need
appears to be for mobility aid technology that is inexpensive, easy to
learn, and not distracting from natural cues. The technology should,
however, display significantly more information than what is available
from natural cues and be able to give a demonstrable improvement in
travel performance.
RECOMMENDATIONS
We can expect further improvements in electronic mobility aids to
be limited less by technological considerations than by two other main
factors: the determination and definition of the information needed by
the traveler and the capacity of the nonvisual senses to process the
information via a suitably encoded display. Compared with these
problems, the development of technology to acquire and encode the
information is relatively straightforward. Solution of the problems,
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in turn, will depend on our ability to evaluate mobility performance
and real needs for information {Leonard and Carpenter, 1973; Brabyn and
Strelow, 1977; Dodd s et al., 19831.
On the basis of this review, we make research recommendations in a
number of areas.
Problem Definition
Information Needed for Mobility
The critical types of environmental information needed for mobility
(and their relative priorities) must be established by experiment,
giving a more concrete starting point for the problem of information
acquisition and display. A preliminary analysis suggests that this
information should include obstacle detection and identification, path
surface discontinuities, shoreline information and other n straight
courses input, and landmark identification.
RECOMMENDATION: Research should be undertaken to establish the
types of environmental information needed to address the problem of
information acquisition and display in the development of electronic
mobility aids.
Research on User Skills
As a prerequisite for electronic aid design, research is needed to
investigate specific aspects of existing user skills, including deter-
mination of the prevalence of echo-location skills among the blind
population and determination whether such skills would be significantly
improved by use of metallic cane tips, improved training methods, or
both.
The importance of these subtle echo-location cues needs to be
determined, since certain electronic aid displays can mask them.
Research is also needed to determine the precise ways in which
different low-vision pathologies affect mobility performance.
RECOMMENDATION: Research should be undertaken on the relationship
between user skills and electronic travel aid design and display
characteristics.
Technology for Display Design and Simulation
RECOMMENDATION: Simulation of information displays should be
developed. Different methods of displaying information for mobility
must be carefully designed to match the sensory systems and tested by
experiment (largely without developing sophisticated hardware). To
achieve this, displays can be simulated manually or with simple
technology, and their effects on mobility performance can be measured.
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Technology for Optical Aids
RECOMMENDATION: Research should be conducted to investigate why
existing aids are rejected as well as the conditions required for
acceptance. These results will be essential to the design and use of
future travel aids.
RECOMMENDATION: The visual requirements for mobility should be
explored fully. Visual parameters to be studied include the necessary
and sufficient sizes and locations of visual f ields and contrast
thresholds for mobility and ocular motility, including the ability to
scan the environment and track moving objects.
Recommendation: Research is needed to study the kinds of image
transformations that will be both useful and acceptable with minimal
disturbance to the user:
Research and development of innovative lens systems is needed. The
Amorphic Lens, described earlier, might perhaps be improved on by using
a nonuniform compression of the periphery that would give priority to
the most important areas of the periphery for mobility. Research is
also needed to determine how much image compression can be tolerated in
a minifier, producing a wider field in which obstacles can be better
detected without destroying the usefulness of the central field in
identifying objects or tracking an aiming point.
Research is needed to study the application of auto-focusing
techniques, such as those found in cameras, to be used in future
telescopic aids.
Further research is needed to investigate both the objective
assessment of glare and the measurement of image degradation as a
function of wavelength composition of the light. These results would
facilitate a rational choice of absorptive filters to produce the most
effective attenuators of glare with the least amount of overall light
loss.
Technology for Information Acquisition
Once the critical information required for mobility has been
established in accordance with our recommendation pertaining to the
identification of information needed for mobility, a wide variety of
technologies should be explored for the acquisition of this information
from the environment.
Optical, Opto-electronic, and Other
Electromagnetic Sensing Systems
The use of miniaturized solid-state video cameras coupled with
miniaturized image processors offers one flexible method for
information acquisition. In addition to optical sensing systems, other
sensing systems based on electromagnetic phenomena may also be
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applicable. These include millimeter radar, infrared and heat sensors,
and magnetic sensors. Light amplification systems can also be useful
· . · ·
In . tow vlslon.
RECOMMENDATION: Researchers applying electromagnetic sensors
should be urged to find a way to process and display the information
auditorially or tactually in an easily interpretable manner. -
Sonic and Ultrasonic Systems
Sound-based sensing systems suitable for information acquisition in
this context may include use of both audible and ultrasonic sound
waves. Appropriate audible signal transmission and reception may
improve echo-location abilities.
RECOMMENDATION: We recommend that research and development
programs be initiated to adopt ultrasonic transmission and reception
systems for both simple and complex degrees of information acquisition,
ranging from simple pulsed transmission and reception to phased array,
variable beam width, focused or unfocused scanning systems.
Furthermore, we recommend that new developments in ultrasonic
technology, currently in research use for spatial sensing by blind
children, be carefully evaluated for possible application to mobility.
New developments in wide-band frequency modulated ultrasonic
spatial sensors (which have a built-in ability to display,
auditorially, a relatively large quantity of information) include
greater resolution, adjustable range, automatic level controls, and the
simulation of the human retinal response by the provision of a narrow
central beam and width (and weaker) peripheral beams that can be
switched off or on at will. These new systems should be thoroughly
investigated to determine their value in new mobility aids.
Information Acquisition for Orientation and Navigation Aids
Considerable research has already gone into the development of
automatic navigation systems for military and civilian applications
(e.g., the navigation of cruise missiles, ships, aircraft, and ground
vehicles). The two essential components of an automatic navigation
system are (1) a digital "map" representation of the geographical
region of interest and (2) a functional module that senses the vehicle
location via some combination of inertial, satellite, or radar
sensors. The two components together might find use as a navigation
system for the blind population.
RECOMMENDATION: We recommend that exploration be made of the
potential application of digital map and positive sensing systems to
navigation and area familiarization for blind or visually impaired
people. Information acquisition technologies that could be applicable
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include inertial sensors, satellite and radio navigation data, footstep
measurement and monitoring devices, and electronic directional devices,
including compasses. Improved and less expensive methods of providing
environmental labels, such as solar-powered coded transmitters or
passive coded reflecting strips, which could be interrogated by
intelligent transceivers carried by the pedestrian, should also be
investigated.
Technologies for Information Display
Auditory Displays
RECOMMENDATION: For auditory information display, the use of
synthesized speech needs to be tested {this can be done by simulation,
as mentioned earlier). Brief verbal messages, at a level of complexity
selectable by the user (or in response to user interrogation) may
provide a means of display for part of the information generated by
acquisition systems.
Speech is a very redundant means of communication. other auditory
codes could well be more efficient {but may require more training).
RECOMMENDATION: Efforts should continue to devise nonverbal
displays having simple, easily learned underlying auditory codes but
from which progressively greater degrees of information can be
extracted as experience accumulates (such as that used in the swept-
frequency ultrasonic family of devices). Simpler coding systems
conveying less information may be useful in conjunction with other
natural or artificial sensory inputs.
RECOMMENDATION: Research and development projects are needed to
investigate the use of externalized or stereophonic auditory displays.
These displays have the potential of providing the user navigational
information in real time both for environmental familiarization and for
inclusion in new mobility devices. These investigations should study
both auditory and synthetic speech displays. The goal of the research
and development effort would be to make the sounds appear to be coming
from different locations in auditory space.
Tactual Displays
Tactual displays can make use of both cutaneous and kinesthetic
information and include tactile maps and simple vibration. Past
experience shows that direct, unprocessed transfer of video images to
large two-dimensional tactile array is not suitable for mobility.
Furthermore, from a technical standpoint, it should be noted that large
tactile arrays have been, to date, unreliable. However, new methods of
coding or preprocessing spatial information before it is presented to
such displays, and new display technology that makes two-dimensional
arrays more technically realistic, should not be ruled out.
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More modest use of tactile displays, such as in one-dimensional
arrays, has proven technically feasible and capable of transferring
considerable information, especially in the field of auditory
substitution. This type of display should therefore be explored, along
with single-point stimulation or variable-frequency vibration. Dynamic
computer-controlled factual maps, should a feasible technology emerge
for their implementation, could be useful in orientation training and
research.
RECOMMENDATION: We recommend that research be continued on new
methods of factual display, emphasizing preprocessing and ease of
interpretation of displayed information. Research and development
efforts should be initiated to investigate the feasibility of new
tactile display technology with the goal of fabricating dynamic
computer-controlled factual maps to be used in mobility training and
research.
Visual Displays
Even the most rudimentary residual visual function may be used for
presentation of environmental information, although not necessarily in
a conventional way. Those with visual function at the level of n light
perception" probably have significant temporal luminance modulation
bandwidth that could be exploited for display of environmental informa-
tion. If an individual has trichromatic light perception, the
possibilities are significantly increased by providing color cues.
RECOMMENDATION: Research should be conducted on novel ways of
presenting information obtained from any visual information acquisition
device to the severely impaired eye. Attempts should be made to permit
the use of head movements in order to avoid the encumbrances of a
hand-held device.
Exploration should be made of the development of opto-electronic
distance magnifiers and locomotion aids, given the existence of
commercially available miniature video cameras and heads-up display
technology being developed for pilots, to determine the usefulness of
these new technologies to enhance the mobility of partially sighted
people. These systems could help solve the problems of optical
leverage with electronic damping of image translation and perhaps
provide image processing tailored to an individual's impairment.
Combination or Multimodal Displays
Combinations of auditory and tactile and visual display technology
may enable greater information display capabilities. A one-dimensional
tactile display, for example, could be used to provide distance or
direction information for nearby objects whose description is given
auditorially (e.g. with a one-word verbal descriptor) after the manner
suggested by Collins and Deering (1984~.
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RECOMMENDATION: Combinations of display technologies should be
explored, in particular combinations of visual displays with auditory
or tactile input for partially sighted people and combinations of
auditory and tactile input for blind people.
Technology for Information Processing
Contributions are anticipated from both signal-processing techniques
and from selected subfields of artificial intelligence. Promising
areas include:
(1) Signal processing--e.g. image processing, including noise
filtering, edge enhancement, and contrast enhancement and
(2) Artificial intelligence--e.g. computer vision, including image
analysis for object identification and contour following for map
correlation; natural language, including voice input, synthesized
speech output, and dialogue management; and inference mechanisms,
including expert systems and script-based situation analysis.
A final comment on the dynamics of technological development in our
society is in order, for technology development has implications for
research in the area of mobility for visually impaired people.
Technology advance has sometimes been defined as a solution in search
of a problem, and it is often cited as a primary cause whenever a
technological device is produced that does not succeed in the
marketplace. It is important to remember that technology advance is
probably inevitable: it can be controlled but not eliminated. The
only way to reduce its negative impact is through better theoretical
and practical understandings of the problems in advance. And that
requires that basic research on several facets of orientation and
mobility be carried out.
RECOMMENDATION: Research should be carried out to study the
feasibility of incorporating contemporary and future electronic
processing capabilities into mobility aids for the visually impaired to
make devices n smarter" and easier to use.
Representative terms from entire chapter:
information acquisition
