Patent GB-912634-A (GB)
Title: Improvements in or relating to the electrical separation of consecutively scanned characters
IPC: G06V30/10
Filed: 1960-01-29
Abstract: 912,634. Automatic character reading. STANDARD TELEPHONES & CABLES Ltd. Jan. 29, 1960 [Feb. 5, 1959], No. 3279/60. Class 106 (1). In automatic reading apparatus for characters which may each be connected with the next by smudges or the like, the characters are scanned in a vertical raster of points, Fig. 1, and the signals entered serially into the stages of a shifting register 6, Fig. 6, having a number of lines and columns to correspond with the scanning raster so that the character is represented in the register as a pattern of electric signals, Fig. 3, and the line of separation between a character and the next is determined either by finding the minimum amount of " black " by comparison between adjacent columns or by finding two adjacent columns at least one of which has a " white " signal in each horizontal position. The normal centring provision consists of means to shift the character pattern vertically and horizontally in the register until the left-hand column is white, the second column has some black and the top row has some black. For this purpose the top row stages 1/1-1/0, Fig. 6, are connected to an OR gate T1 the output of which opens gate T3 and the second column stages 1/2-12/2 are connected to an OR gate T2 the output of which sets a flip-flop FF2. The flip-flop FF2 is connected to another FF1 and its setting is shifted into it as the character pattern is shifted to the left in the register. A proper separation between characters gives a column of " white " stages which cause flip-flop FF2 to be reset through OR gate T2 and the next column shift resets flip-flop FF1 to the " white " condition. If the flip-flop FF2 is again set, owing to parts of a character appearing in the second column, and if the OR gate T1 is giving an output, gate T3 passes a signal to gate T4. Character recognition circuits 10 one for each character are each connected to the register stages. If one of them gives an output showing that a character has been recognized, the gate T4 opens to allow a signal to appear at terminal 11 to indicate that a recognition has been made. If the pattern is not recognized, a gate T5 passes the signal to reset FF2 to " white " so that after a left shift FF1 becomes " white " and a second recognition becomes possible. In the case of the " 5 " in Fig. 3 the smudge at the left-hand side would cause the first recognition attempt to be made with the smudge in column 2. After the failure of this the left shift brings the character to the centred position and owing to the injection of an artificial " white " in the smudge column a correct recognition is made. Similar re-positioning can be made in the vertical direction. End of character found by difference, between columns.-If these two methods fail owing to the complete absence of a white column between two characters, the line of separation is determined by finding a condition where the number of " black " stages in column 3 is greater than the number in column 2. For this purpose, resistors R1, R2 are connected to each stage of these two columns and voltages are derived at P1 and P2 which are proportional to the number of " black " stages in each. A transistor Trl conducts when P2 is greater than P1. This occurs on the left-hand side of most characters if the area of smudge is less than the area of character (in Fig. 3, four stages and five stages, respectively). The conduction of transistor Trl passes a signal through OR gate T9 and pulse shaper 12 to reset FF2 to the " white " condition (although column 2 is at this time occupied with the smudge). A recognition then becomes possible on the next step. To prevent this circuit injecting a " white " or separation signal at the wrong time the number of steps during which the character is passing through column 2 is counted in a counter 13 and the transistor circuit is allowed to produce the difference signal only when, say, five column periods have passed. Instead of depending on a simple difference the separation signal may be derived from a minimum of " black " stages in one column compared with the neighbouring columns. " Zig-zag " method.-The bottom two stages of columns 2 and 3 may be connected to an AND gate T7 to set a flip-flop FF3 when both stages are " black " and close gate T8 to prevent the resetting of FF2 to " white " Since the signals are entered and passed through the register in serial form the whole pattern moves vertically in the register and reappears at the bottom displaced one column to the left. At some time therefore the contents of columns 1, and 2, Fig. 5b, pass through stages 12/2 and 12/3 Fig. 6. If one or the other remains " white " for a complete column shift, the condition of columns 1 and 2, Fig. 5 b is present and the next column pulse resets FF2 to indicate that column 1 (in Fig. 5b) is to be taken as the separating column for centring purposes.