"That the blind may see" is an ageless desire in the human heart, a prayer often equated with the humanly impossible - and often applied to blindness of spirit. But to the non-sighted, the metaphor is one of degree rather than one of futility, for the blind do see with their fingers, with their canes, and with any other sensory power they have. We usually think that a functional prosthetic device for a blind person must be micro-surgically implanted in his or her optic nerves or cortex. But the blind for decades have used the sensory nerves of their fingers to read Braille and to explore their world by manually studying the space around them with their hands or canes. To these people, their brain has become resilient enough to allow them to experience aesthetic pleasures, and to enjoy discovering their visual world without the benefit of light sensing organs
The theory of tactile sensory substitution dates back to the early 1900s, but it was not until the 1960s that electronics had matured to a point where significant efforts could be made to put this theory to more practical use. In the 1960s, Dr. James Bliss and his colleagues developed the Optacon, a tactile sensory substitution reading aid for the blind. The Optacon consists of a 6x24 element photodiode (light-sensitive) array that is mapped onto a 6x24 matrix of vibrating reeds, where the user places his finger to sense the image picked up by the light-sensing array. Subjects trained on this device were able to achieve reading rates of 60 words per minute.
Also in the 1960's, at the Smith-Kettlewell Institute of Visual Science, Dr. Bach-y-Rita and his colleagues developed a large electromechanical array of 400 points mounted in a dental chair which would transmit patterns of vibration onto the back of a person sitting in the chair. The patterns of vibration were dictated by the images sensed by a television camera under the control of the person in the dental chair. If the camera was directed towards a white vertical line on a black background for instance, the person would feel a vertical line on their back. If the camera were moved to the right, they would feel the line move correspondingly on their back. Although such a system did not have anywhere near the ability of the human eye to gather visual information, it showed that the brain was indeed capable of perceiving visual information through the skin (Brain Mechanisms in Sensory Substitution, by Paul Bach-y-Rita).
Because electro-mechanical components are noisy, costly, consume a lot of electrical power, and have very limited reliability, efforts were made to develop electrical tactile stimulators. While these efforts were able to overcome many of the problems associated with electro-mechanical stimulators, new problems with comfort of sensation and skin irritability, and oftentimes even skin burns surfaced. These problems would have to be overcome before electrical stimulation could be practically used in tactile feedback applications.
Enter ForeThought Development
With the tremendous scientific advances made in electronics, materials and manufacturing techniques since the 1960's, we endeavored to find a way to develop a multi-channel electrotactile system that would be able to stimulate the skin in a safe and comfortable manner. When ForeThought Development began its most recent effort to produce a high density electro-tactile array for computer graphics perception under National Institutes of Health funding, its investigators had amassed decades of cumulative years of experience advancing and evaluating this technology. Some of the research described here was funded under various grants from the National Eye Institute of NIH, some was funded by equipment purchases, and some was purchased with the acquisition of an existing sensory-research company.
During our initial research efforts we developed tactile feedback systems for our own in-house development program. As we made progress, there was an increasing interest in our work by other organizations, and we began to perceive the growing need for a user-friendly tactile feedback system that could be used by others to meet their specific research and development needs.
Important accomplishments and features of the Videotact
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