Patent GB-1093130-A (GB)
Title: Character reader
IPC: G06V30/184
Filed: 1965-12-17
Abstract: 1,093,130. Character recognition. RADIO CORPORATION OF AMERICA. Dec. 17, 1965 [Jan. 4, 1965; Jan. 8, 1965], No. 53628/65. Heading G4R. A character reader detects the size of vertical strokes and which of two such strokes is higher in position. A slotted disc scans a character along a plurality of vertical scans in turn. Pulse width discriminators 56, 58 provide short vertical stroke SVS and long vertical stroke LVS signals when block signals at least 5 and 11 intervals long respectively are produced. (There are 14 intervals per scan). A zoning circuit 70 produces a character dependent grouping of the scans into zones as follows. The first stage of a shift register 92 was set to 1 after the preceding character was finished with, to indicate the right zone RZ. After appearance of a short stroke signal SVS. absence of both stroke signals SVS, LVS during a subsequent scan will the step the 1 along to set a flip-flop 94 to indicate centre zone CZ. The 1 is now stepped along once per scan and on the third scan after setting of the flipflop 94 will reset it, unless a stroke signal SVS or LVS has previously appeared during one scan in the centre zone and not during the next scan when the latter event will reset the flip-flop 94. Resetting of the flip-flop 94 causes an AND gate 104 to indicate left zone LZ. The zone signals RZ, CZ, LZ are used in conjunction with the stroke signals LVS, SVS to set flip-flops 112, 114, 116, 124, 126, 128 indicating the presence of long and short strokes in the three zones respectively. In a short white gap detector 140, a pulse width discriminator 144 receives an input pulse during white signal in the centre zone provided this follows black signal in the same scan. If the input pulse exceeds two intervals, a four interval pulse is applied to an AND gate 158 which, if black signal is currently present, will increment by one a two-stage binary counter. A count of two will prevent further incrementing and will produce a short white gap indicating signal SWG. Thus, a short white gap can be detected in one scan if three horizontal strokes are present or in two scans if the character is distorted enough to have one horizontal stroke missing. A right -stroke higher RSH signal or its negation is produced by causing a first ramp generator 172 to run down from the time of appearance of the first short vertical stroke signal SVS to the end of the scan in which it appears and causing a second ramp generator 180 to run down from the time of appearance of the first such stroke signal SVS to occur after the right zone until the end of the scan in which it appears. Comparison 188 of the generator 172, 180 outputs determines which stroke is positioned the higher. The character is identified from the feature signals, viz. short and long stroke in right, centre and left zone signals SVR, SVC, SVL, LVR, LVC, LVL, the short white gap signal SWG and the right stroke higher signal RSH, at the end of the first all-white scan subsequent to the first short vertical stroke signal, which set a flip-flop 66 to indicate the character had begun. During each scan, three clock pulses were produced, one at the beginning SSP and the others near the end TP1, TP2.