Electronic Travel Aids New Directions for Research (1986) / Chapter Skim
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6: The Technology of Electronic Travel Aids
6: The Technology of Electronic Travel Aids
Pages 67-80
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From page 67... ...
ly to cover the width of the traveler's body. The minimum distance or range over which this information is needed is a comfortable stopping distance at normal walking speed.
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From page 68... ...
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)
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From page 69... ...
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)
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From page 70... ...
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)
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From page 71... ...
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.
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From page 72... ...
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.
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From page 73... ...
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.
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From page 74... ...
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.
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From page 75... ...
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.
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From page 76... ...
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.
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From page 77... ...
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.
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From page 78... ...
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)
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From page 79... ...
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.
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From page 80... ...
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.
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