Patent GB-1060920-A (GB)
Title: Character scanning apparatus
IPC: G06V10/10
Filed: 1965-11-22
Abstract: 1,060,920. Character recognition. INTERNATIONAL BUSINESS MACHINES CORPORATION. Nov. 22, 1965 [Dec.18, 1964], No. 49453/65. Heading G4R. Character scanning apparatus comprises a scanning device, means for measuring the centreline height of a character to be scanned, and means for utilizing said measurement for controlling the vertical limits of the scan. In character recognition apparatus, bit signals from vertical scans of a character by a cathoderay tube are passed to a shift register (100). The following conditions are looked for in turn during each scan, detection of a condition setting a corresponding latch (154, 158, 160, 162, 164) and resetting the latch of the preceding condition: (a) the pattern X00011 in the shift register (X being a " don't care " bit) indicating the crossing of the lower edge of the lowest line of the character; (b) the pattern XXXX11 indicating the crossing of the upper edge of the lowest line; (c) a count of 14 bit segments in a " skip " counter (225) enabled to count clock pulses while conditions (a) and (b) are satisfied; (d) the pattern X00011 indicating the crossing of the lower edge of the highest line of the character; (e) the pattern XXXX11 indicating the crossing of the upper edge of the highest line. If conditions (b) and (e) are not satisfied in five bit times after satisfying conditions (a) and (d) respectively, the (a) and (d) latches (154, 162) are reset by an ABORT signal following on recognition of pattern 11XXX1 or 1X1XX1 and conditions (a) and (d) have to be satisfied again if this scan is to be used for the purpose described below. In addition the (a) condition latch (154) can only be set during the first half of the scan. While the condition (a) and (d) latches (154, 162) are set, a " twice centreline " counter (250) counts one each bit time and while the condition (b) and (c) latches (158, 160) are set, it counts two each bit time. Provided the condition (e) latch (164) is set shortly following the end of a scan, six " centreline " counters (402, 410, 418, 426, 434, 442) are then enabled to respond to the " twice centreline " counter (250) as follows. Six lines (N15 to N20) are provided corresponding to " twice centreline " counts of 15 to 20 respectively. If the " twice centreline " count is even, the line corresponding to half the count is marked, whereas if it is odd the two lines corresponding to adjacent numbers which sum to give the count are marked. Each line (N15 to N20) corresponds to a respective one of the " centreline " counters and when marked will increment by one all the " centreline " counters not at zero, provided the counter corresponding to the line is at zero, whereas if this counter is not at zero, it (alone) is decremented by one. After a number of scans covering the whole character as recognized by a scan counter (477), the identity of the " centreline " counter at zero indicates the maximum character centreline height and a corresponding number is entered into a 4-stage binary " intermediate control " counter (550). The latter and a similar " control " counter (570) which was preset to ten, are then incremented until the former (550) reaches 0000, provided the circuitry had attempted to set the lowest order trigger (551) of the " intermediate control " counter (550) to either 1 or 0. The " control " counter reading is converted to an analogue voltage in weighted resistors and used to augment a standard CRT deflection voltage subsequently used for recognition scanning.