Patent GB-1324727-A (GB)
Title: Centre referenced character identification
IPC: G06V30/224
Filed: 1971-04-19
Abstract: 1324727 Character recognition systems RECOGNITION TERMINALS Inc 19 April 1971 [17 April 1970] 27222/71 Heading G4R Printed or hand-written numerals which are to be read by a machine are each impressed on a field having a bar which intersects the character. Fig. 2 shows numeral 2 impressed on a rectangular field having a central bar 13. The field is scanned from left to right in successive vertical strips, the machine operating to determine whether a bit from the scanner is black, or is an enclosed white, i.e. is a white bit lying in an area bounded continuously by the centre bar and the character as are areas 14, 16 or is a non- enclosed white, e.g. as in areas 15, 17. This information, together with other data referred to below, allows the character to be identified. During the scan of a vertical strip of the field the black/white bits from the scanner 10, Fig. 1, are passed to a logic unit 21. As the scan proceeds from top to bottom of the strip this unit performs a first transformation in which each b/w bit in the strip (e.g. 48 bits) is converted to 2-bit form, each such pair indicating whether the b/w bit is (a) back, (b) white but possibly lying in an enclosed area, as indicated by the presence of a black bit above and to the left of the current bit, or (c) white and not enclosed, as indicated by the absence of a black bit above or to the left of the bit. Those bit-pairs are stored in register 24, and in the interval between the end of the scan just completed and the scan of the next strip of the field the bit-pairs are fed back to the logic unit 21. By inspection of the bit-pair lying below each b-type bit pair (possibly enclosed) it is determined whether the b-type pair shall be replaced by a c-type pair (non-enclosed white) or a d-type pair indicating that the bit is totally enclosed. The set of a, c, and d type signals developed following the scan occurring immediately prior to the detection of the centre bar is fed to a register 25. During the scan of the portion of the numeral to the right of the centre bar the signals from the scanner are stored in memory 23. When the end of the field is detected the scan strips are read out in reverse order to logic unit 21, and successive scans are processed as described above to provide a second set of a, c and d type signals to register 26. The two sets of signals represent the respective projections of the left and right portions of the numeral on to the centre bar 13 and indicate the vertical extent of the closed and non-enclosed parts. The registers are associated with circuitry Fig. 7 (not shown) which, for each numeral develops signals on lines LTW7, LTF7 &c. indicating the position of enclosed areas to left and right of the centre bar. These signals pass to recognition logic 41. To accommodate hand-written numerals the recognition logic 41 also receives a signal from unit 35 indicating the maximum number of intersections of the numeral with one of the scan strips to the right of the centre bar. It also receives a signal from unit 27 indicating the number of intersections with the centre bar, and from unit 34 it receives further signals. These signals depend upon the outputs of counters 30- 33 which, for left and right projections, determine the number of black bits above and below the lowest intersection with the centre bar. Unit 34 determines the magnitudes of the ratios of the counter output, and provides signals which eliminate ambiguity which may otherwise exist when scanning numerals 1, 4, 9, or 10.