Patent GB-936032-A (GB)
Title: Character recognition apparatus
IPC: G06V30/162
Filed: 1959-12-23
Abstract: 936,032. Character-recognition systems. INTERNATIONAL BUSINESS MACHINES CORPORATION. Dec. 23, 1959 [Dec. 29, 1958], No. 43641/59. Class 106 (1). General.-Elemental areas of a character are examined in a plurality of adjacent scans to produce signals indicating whether a black or white region is being scanned, successive signals are integrated and applied to a threshold device giving an output representing black for example, if the value of the integrated signal over a complete scan of an elemental area exceeds a predetermined threshold value, and sample signals are derived to indicate the nature of at least one sample part of each elemental area, these sample signals being used in conjunction with the signals integrated over a complete scan of the elemental area to determine whether the area should be regarded as being black or white when the integrated signal fails to reach the threshold level. First embodiment. - A character is scanned in a series of narrow vertical rasters each comprising k elemental areas, each area being examined by four horizontal scans. The output of photomultiplier 15, Fig. 1, is clipped to produce trains of two-state signals Vc representing black or white. Pulses S, R are produced at the end of each horizontal scan and vertical raster respectively, a pulse S4 is produced for the duration of every fourth horizontal scan, and pulse Z marks the end of every fourth horizontal scan. Pulses S define areas over which successive vertical rasters overlap. The signals Vc are applied to integrator 31, Fig. 2, which supplies clippers 43, 45. If the elemental area scanned is more than 50% black, trigger 53 is set and the output Vs is " black." The signals Vs are supplied to character recognition circuitry and also to a shift register or other storage device (e.g. delay line or magnetic tape or drum) which provides signals at terminals Ak, Al indicating the previous " black " or " white " decisions made in respect of the elemental areas horizontally and vertically adjacent to the area being scanned. The vertical edge which overlaps the previouslyscanned horizontally adjacent area is examined by integrator 33 and clipper 65 (set at 15% black), and the leading horizontal edge is examined by integrator 35 and clipper 77 (also set at 15% black). If the area is between 25% and 50% black and (a) the threshold level of clipper 65 is not exceeded, or the horizontally adjacent area is not black, and (b) the threshold level of clipper 77 is not exceeded, or the vertically adjacent area is not black, then gate 61 is not inhibited by inverter 63 and Vs is again "black." Second embodiment, Fig. 4.-In this system the vertical rasters do not overlap. The signals Vc are applied to a delay device 115 introducing an overall delay of one horizontal scan interval and having tappings. 117, 119. Trigger 134 is set if two black regions in the third and fourth horizontal scans lie directly one above the other, and trigger 135 is set if three black regions (spaced by amounts determined by tappings 117, 119) occur in any horizontal scan (or two adjacent scans). If the area is more than 75% black, trigger 113 is set and Vs is " black." If the area is between 50% and 75% black, trigger 111 is set and if (a) trigger 135 is not set and Ak indicates " black," or (b) trigger 134 is not set and Al indicates " black," then gate 137 is not inhibited and Vs is " black." If the area is between 25% and 50% black, trigger 109 is set, and if (a) trigger 134 is set and the inverted signal NAk indicates " white," or (b) trigger 135 is set and the inverted signal NA1 indicates " white," or (c) triggers 134, 135 are both set then Vs is again black.