Patent GB-1153012-A (GB)
Title: Apparatus for Determining the Boundary Between Two Touching Line Patterns
IPC: G06V30/10
Filed: 1967-01-18
Abstract: 1,153,012. Character recognition. INTERNATIONAL BUSINESS MACHINES CORP. 18 Jan., 1967 [19 Jan., 1966], No. 2573/67. Heading G4R. Apparatus for determining the boundary between two touching line patterns comprises means for defining a zone in which the boundary is to be determined, means for recognizing predetermined characteristics in the directions of the lines within the zone, the characteristics denoting the existence and position of a boundary, and means for storing a representation of the position of the boundary. A flying-spot-scanner curve-follower follows round the outline of a character two or more times, the horizontal and vertical deflection voltages (excluding a " jump and search" component of each which is constant during outline following, and after filtering to remove dither voltages) being fed to a matrix resolver (both voltages), slope detector (both voltages) and segmenter (only the horizontal voltage). During the first follow, the matrix resolver establishes the character size and produces voltages to divide the character into a 4 x 5 matrix. On subsequent follows, the matrix resolver produces signals specifying which matrix position the scanner is in at any given time. These signals together with direction signals from the slope detector (specifying the one of eight sectors that the direction of the scanner beam lies in) are fed to feature detecting circuits feeding character recognition logic. During the first follow, the horizontal deflection voltage mentioned above is compared in two voltage discriminators (Fig. 4A, not shown) in the segmenter with constant voltages and as long as it lies between them, the segmenter is enabled to look for any of a plurality of predetermined sequences of directions from the slope detector to detect (Fig. 4B, not shown), a boundary between two touching characters. If such a boundary is detected, a signal is produced at 94a in Fig. 3 to set a flip-flop 66 and to cause a capacitor 65 to be charged to the current value of the (full) horizontal deflection voltage of the scanner (i.e. the boundary position), applied to the segmenter at 13a. The same boundary may be detected several times, corresponding to different ones of the predetermined sequences of directions. If so, the position of the last detection is finally retained. During the first follow, also, capacitor 70 is charged to the value of the horizontal deflection voltage at the left extreme of the left character of a touching pair (or the left extreme of a sequence of more than two touching characters, or a free-standing character, as the case may be), the deflection voltage increasing with movement to the left. Also, capacitor 78 is charged to the value of the horizontal deflection voltage at the start of the follow, i.e. at the right extreme of the character pair or &c., by charging the capacitor to agree with the voltage at 13a until a " first hit " signal 1H is produced. In the case of two touching characters, for example, the first follow is round the pair. Subsequent follows for the right-hand character of the pair are then done before follows for the left-hand character. During these follows round the right-hand character (but not during the first follow, round the pair) whenever the deflection voltage at 13a exceeds the " boundary " voltage on capacitor 65, difference amplifier 68 enables AND 85 to inhibit the feedback from the photomultiplier in the scanner so that the system effectively acts as if it sees just white (background) to the left of the boundary. During all follows round the left-hand character (including the first follow, round the pair), whenever the deflection voltage falls below the voltage on capacitor 78 (which at this time represents the boundary between the two characters-see below), difference amplifier 79 causes AND 85a to similarly inhibit the feedback. After dealing with the right-hand character, an end-of-character signal EOC from the recognition logic causes the scanner beam to be deflected with so-called " jump " voltage until the horizontal deflection voltage at 13a equals the " boundary " voltage on capacitor 65, when difference amplifier 68 causes AND 67, enabled by the set state of flip-flop 66, to terminate the jump. The lefthand character is now followed as described If the first character were free-standing, the flip-flop 66 would not have been set and AND 72 would have been enabled by it to terminate the jump when the horizontal deflection voltage at 13a equalled the voltage on capacitor 70 representing the left boundary of thefirst character, as determined by difference amplifier 71. The jump is followed by a raster " search " to locate the next character.