Kocher, D. G.

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XVIII. CIRCUIT THEORYProf. S. J. Mason Prof. R. D. Thornton D. G. KocherProf. H. J. Zimmermann J. T. Andreika B. J. LeonProf. J. Granlund T. G. Stockham, Jr.A. SENSORY AIDS PROGRAM: READING MACHINESIn connection with the Sensory Aids program, a study was made of previous readingmachines for the blind, and also of proposed methods and devices that might enable blindpersons to read printed text. As a result of this study, we concluded that our initialefforts would be directed toward the development of a machine for complete characterrecognition.In the terminology of the sensory aids field, a "recognition" reading machine makesthe decision of identification of an input character from its input geometrical configura-tion, and presents this identification to the operator of the machine. A different typeof reading machine is the "direct-translating" machine, in which no attempt is madeto have the machine make the character identification, but rather, its function is onlyto transform (translate) geometrical proportions of the character that is being scannedinto modulations of its output signal, which are usually auditory or tactile. Since inthe direct-translating machine the information content of the output and input is thesame, and because of the redundance in the geometry of the printed alphabet, the infor-mation content at the output far exceeds the capacity of the aural or tactual channels atall but the lowest reading speeds. Several different types of direct-translating readingmachines have been built and tested, the earliest (1) of which was constructed in 1914,and, indeed, consistent reading rates higher than 20 words per minute have rarely beenattained with these machines (2).The recognition machine, however, processes the input-character geometry suf-ficiently to permit much higher reading rates, according to the output medium selected;for example, if the output is in the form of syllables, the ultimate presentation to thereader might be synthesized speech, transmittible at rates of several hundred wordsper minute.The recognition machine that is envisioned at the present time is composed of threefundamental parts: (a) the input head, or scanner; (b) the detector; and (c) the logicsection (see Fig. XVIII-1).The scanner is a mechanical-optical system that, for the purposes of explanation,repeatedly sweeps two small adjacent spots of light vertically through a single line ofprint. These illuminated areas are small compared with the size of the character thatis being scanned, and are arranged horizontally (see Fig. XVIII-2). The reflected lightfrom each scanning spot is separated from that of the other spot and fed into separatephotodiodes. The vertical sweep is automatic, and the horizontal motion is suppliedby the operator.121(XVIII. CIRCUIT THEORY)HAND-HELDSCANNERLOGICDETECTOR SECTON OUTPUTPRINTED PAGEFig. XVIII-1. Block diagram of recognition machine.The detector utilizes the outputs of the photodiodes to determine, principally, threeimportant characteristics: (a) the length of vertical lines, (b) the number of nonverticallines crossed, and (c) the slopes of each of the nonvertical lines crossed, in each verticalsweep. For instance, scanning a capital "N" would result in the following sequentialinformation: the presence of (a) a long vertical, followed by (b) a single line-crossing(in a vertical sweep), with a negative slope, followed by (c) another long vertical. Theoutput of the detector consists of a number of binary outputs, a certain combination ofwhich is presented to the logic section upon the completion of each vertical sweep by theFig. XVIII-2. Path of scanning spots as scannerof Fig. XVIII-1 is moved across\ the capital letter "N"SCANNING \SPOTSscanner. The logic section then utilizes the sequential output of the detector to identifyeach character as the scanner is moved horizontally across the line. An attempt isbeing made in the design of the detector to eliminate errors resulting from changes inthe type-face style that is being scanned.Note that the scanner and detector alone might be used as the basis for a readingmachine of a type that is intermediate between the recognition machine and the direct-translating machine. The addition of some form of simple logic after the detector, topresent the detector output directly to the reader only when the detector output changes,would reduce a great deal of the redundancy that is inherent in direct-translatingmachines. Another type of intermediate machine might be one that presented only cer-tain meaningful, preselected combinations of the detector output to the reader.Construction of the scanner and detector is now going on. Work on somewhat similarreading machines (3) is being carried on elsewhere, with different applications inmind (4). This investigation has the specific objective of determining whether or not arecognition machine can be made practicable for blind people.D. G. Kocher122(XVIII. CIRCUIT THEORY)References1. F. d'Albe, On a type reading optophone, Proc. Roy. Soc. (London) 90A, 373-375(1914).2. P. A. Zahl, editor, Blindness (Princeton University Press, Princeton, N.J., 1950).3. D. H. Shepard, B. F. Bargh, and C. C. Heasly, Jr., A reliable character sensingsystem for documents prepared on conventional business devices, IRE WESCONConvention Record, Part 4, 1957, pp. 111-120.4. A bibliography on reading machines has been compiled by the Research and Devel-opment Division, Prosthetic and Sensory Aids Service, Veterans Administration,252 Seventh Avenue, New York, N.Y.123

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