Tactile Television - Mechanical and Electrical Image Projection

The feasibility of communicating pictorial information through the skin has been demonstrated. A tactile television system has permitted blind subjects to determine the position, size, shape, and orientation of visible objects and to track moving targets. The system comprises 1) a vidicon camera utilizing a zoom lens, 2) a digital switching matrix to sequentially connect each element of the photocathode surface through a single video amplifier and signal conditioner to each of the 3) 400 tactile stimulators in a 20 × 20 matrix in contact with a 10-inch square of skin. This image-projector matrix impresses on the skin a two-dimensional vibrating facsimile of either the silhouette or the outline of a visible object. The single-channel swept system exhibits inherent economies when a great number of picture elements is to be processed. Since the fovea of the human eye subserving the central two degrees of detailed vision is comprised of cone cells in a matrix about 200 receptors across, the present 20-line system permits picture transmission with a linear resolution about one-tenth that of the fovea, and has proved adequate for the recognition of human faces. Calculations indicate that the input capacity of the skin of the trunk should compare favorably with that of the fovea. We have determined the electrical-stimulus parameters for painless stimulation of the sensation of mechanical vibration with small electrodes in a closely spaced matrix.