Patent GB-880785-A (GB)
Title: Character recognition system
IPC: G06V30/146
Filed: 1958-12-30
Abstract: 880,785. Automatic character reading. INTERNATIONAL BUSINESS MACHINES CORPORATION. Dec. 30, 1958 [Dec. 30, 1957], No. 42088/58. Class 106 (1).  In an apparatus for sensing and recognizing printed characters the characters are scanned and means operating in synchronism with the scanning means advance the signals into a storage matrix 19, Fig. 1, so that the character shape is represented by a pattern of signals, recognition circuits 31 connected to the matrix responding when the pattern is properly located in the matrix. The sheet 1 carrying the character 2 is passed by feed rollers 4, 5 under a series of sensing elements e.g. photo-cells or magnetic reading heads 15 if the character is magnetic. There are 18 sensing elements H1- H18, Fig. 2, covering a broad scan over the area likely to be occupied by the character. This allows for considerable misalignment, the character being covered by only nine of these elements. The lines from the sensing elements are connected through Or gates OR1-OR9 in two groups of nine, to nine channels SC1-SC9 through which the sensed signals pass to the store matrix 19 which consists of 9 X 5 shift register stages. For synchronization a magnetic drum rotates with the feed rollers and timing marks thereon produce clock signals in head 23 which pass to syn-  chronizing circuits 25 controlling circuits 27, 29 governing the horizontal and vertical shift of the pattern in the shift register matrix. Horizontal and vertical control.-Signals from head 23, Fig. 2, are amplified at 43 and applied to a mono-stable unit 45 the output of which on terminal H controls horizontal shift of the pattern into the store as the character passes under the sensing elements. The output from unit 45 is also inverted and provides on terminal H a negative pulse. The clock pulse also sets a trigger 49 controlling a free-running multivibrator 51 which produces pulses while the trigger is set. These pulses are counted in a trigger chain 53, 55, 57 and after a count of eight the trigger 49 is reset by trigger 57 to stop the multivibrator. After each clock pulse, therefore, a group of eight pulses is supplied and applied via the monostable unit 59 to the vertical shift control terminal V, the signal being inverted to form a corresponding negative pulse on terminal V. The shift register matrix.-The matrix store consists of nine rows of five trigger circuits, all triggers being connected to the horizontal and vertical shift lines H, H, V, V. A vertical shift pulse causes the contents of each trigger to advance to the trigger above it in its column, the top trigger being connected to the bottom one of the column so that the contents of a column can circulate. A horizontal shift pulse advances the contents of each trigger to the trigger in the adjacent column, not in the same row but in the row above. The horizontal shift pulse therefore causes a diagonal shift of one column and one row. Since after each horizontal shift pulse there are eight vertical shift pulses, the contents of each column circulate and the pattern signals are effectively displaced one step to the right remaining on the same level. As the character is sensed the pattern moves across the matrix in synchronism being circulated vertically between horizontal steps. At some time in this process, before the pattern passes out of the store, it will occupy the top seven rows as shown for numeral " 2 " in Fig. 5a and at this instant one of the recognition circuits connected to certain shift register stages will respond to the pattern present. Recognition.-The recognition circuits use combinations of three out of four expected signals at predetermined locations and as a check, the absence of signals at other locations. The combinations for " 2 " are shown in the table of Fig. 5. There are three combinations of locations where signals should be present, i.e. " black " positions and one of locations where signals should be absent, i.e. " white " positions. The first black combination 1B is of positions A2, B1, E2 and E3. The second, 2B, is concerned with positions on the diagonal line A7, B6, C5 and D4 and the third, 3B, with position on the base: A7, B7, D7 and E7. The white combination is of points A5, A6, E5 and E6. As shown in Fig. 6, signals from these stages are gated together in fours e.g. stages A2, B1, E2 and E3 are connected in threes to And gates 111, 112, 113 and 114. If any three of the stages have a signal one of the gates will pass an output via Or gate 115 to And gate 117. Or gates 122 and 128 pass signals if at least three out of the four signals are present for combinations 2B and 3B. Signals from stages A5, A6, E5 and E6 representing the white combination W are inverted and applied to gates 134-137 in the same way. The And gate 117 needs four combination signals, an " S " signal and a " DIH " signal before it can produce an output signifying that character " 2 " has been recognized. The S signal is derived from the circuit of Fig. 2 by delaying the horizontal or vertical shift signals. This ensures that the triggers are properly set after a shift before the gate 117 can open. The DIH signal is derived from the read-out and checking circuit and it ensures that the output storage and checking circuits have had time to operate in respect of the previous character before the present character is applied to these circuits. The DIH pulse, after the first character, is provided by delaying the signal appearing at the outputs of the latches, these being combined by an Or gate. Checking.-When a character is recognized an output appears on the corresponding line, e.g. 2LO, Fig. 6. These signals are temporarily stored on latches and the outputs are applied to a summing amplifier connected to two threshold devices. One of these responds if no character is recognized to give a signal on a " blank " line and the other responds if more than one character is recognized and this prevents read-out from the latches. Alarms may be operated also. Scanning by optical dissection.-In the form of Fig. 8 the image of the character which is illuminated by lamps 191, 192 is dissected in a series of vertical cuts by a rotating slotted disc 195 co-operating with a vertical slot 194. The light passing through the slots is received by a photo-cell 201. Timing pulses are derived from magnetic drum 205 rotating with the disc. The data appearing serially from the photo-cell is amplified and entered in the top left-hand stage A1 of the shift register matrix. The shift is downwards and, when the next scan through the character is about to be made, horizontally into the next column. Thereafter the pattern circulates between horizontal steps as before until it is properly positioned for recognition. Specifications 710,554, 806,457 and 874,709 are referred to.