Patent GB-1126603-A (GB)
Title: Improvements in or relating to apparatus for use in the automatic recognition of characters
IPC: G06V30/146
Filed: 1965-09-28
Abstract: 1,126,603. Character recognition systems. SIEMENS A.G. 28 Sept., 1965 [29 Sept., 1964], No. 41104/65. Heading G4R. In character recognition apparatus, a character positioned in a window is scanned by columns and the scanning signal elements obtained are stored, the number of columns crossing the window is counted and on detection of the first of these columns which does not cross the character (the character merges with the window border at the leading edge) the stored elements are sent for further processing. Referring to Fig. 2, scanning signal elements arrive on line n and are stored in delay memory RR. A memory ZS holds a number for each horizontal row perpendicular to the scanning columns, giving the number of consecutive " zeroes " encountered in the row. As each column is scanned, the numbers are read-out in turn, incremented by one (in the case of a " zero " scanning element) or zeroized (in the case of a " one "), and then restored in memory ZS and passed to a comparator Vgl. Here, the number is compared with the contents of a memory WM and replaces the latter if greater (unless the end of the character has been reached, and provided the scanning signal element was a " zero ") under control of blocking gate GOgr. A unit FY (details in Fig. 6, not shown, and as in Specification 1,126,601, which is referred to) produces signals on lines gf and sgf when a column is scanned having a number of zeroes within predetermined limits, viz. a characterfree column. Providing these signals are absent, a blocking gate G1 responds to a " one " scanning signal element by setting memory WM to a value corresponding to the maximum expected width of a character. At the beginning of the column following the first character-free column (after the character), AND-gate Gla sets bi-stable LA, a signal Sp occurring at each column beginning. A circuit ZY (details below) produces a signal on line gz in response to the rear boundary of the character. AND-gate Glaz responds to (indirectly) shift the contents of memory WM to a counter Zxza (via gate Gwm) and increment the counter by one for each subsequent column (via gate Gsp). When the counter capacity is reached, a bi-stable XZ is set to close a switch Gnx in the output of memory RR to allow the scanning signal elements to pass to recognition circuitry, provided a switch Gnxy is also closed. The latter switch is closed by a signal on line yz produced by unit ZY only for those times in each column when the character is being passed (thus cutting off the upper and lower borders of the window). Scanning signal elements from the left border of the window and the first column in the window are also lost due to the open state of switch Gnx when they emerge from the memory RR. A bi-stable LFZ (bottom, Fig. 2) and associated circuitry deals with a character not merging with the window border on the leading edge. Unit ZY.-Referring to Fig. 3, this unit receives scanning signal elements after a onecolumn delay on line n-1, signals from comparator Vgl on lines gr, gl, a level on line sgf from unit FY as soon as a character-free column has been reached, and " window " signals on lines gyf and yf from unit FY specifying the time position of the window within a column. Assuming a character touching the leading window border but not touching the upper and lower borders, when the upper level of the character is reached in the first column after the character, disappearance of outputs from the comparator causes the output of a gate GO wmf to disappear. Detection of this change by a differentiator DWS, together with presence of the window signal causes a gate Gof to set a bi-stable Sof which enables a gate Glz. When the lower level of the character is reached, reappearance of the comparator outputs produces an output from gate GO wmf which produces an output from gate Glz to OR gate OGz, and resets bi-stable Sof. Alternatively if the character touches the lower window boundary, the set state of bi-stable Sof and disappearance of the window signal produce an output from gate Gluz. Alternatively if the character touches the upper window boundary, no output from gate GO wmf together with appearance of the window signal causes blocking gate Goa to set bi-stable Soa to enable gate Gloz to pass the subsequent output from gate GO wmf (the latter resetting bi-stable Soa). A further gate Gz and associated circuitry is provided to deal with characters not in contact with the front window border. OR-gate OGz receives inputs from gates Gloz, Glz, Gluz, Gz. Bistables Soa, Sof produce a signal level from OR- gate OGp10 while a character is being passed during the first column after the character, and while this level is present, counter Zp10 counts clock pulses. If the count is within predetermined limits (corresponding to a full character), a bi-stable Sp10 enables a gate GZ to pass an output from OR-gate OGz. The levels (duration-significant voltages) occurring from OR-gate OGp10 were counted in a ring counter VZ and the positions reached on outputs from OR-gate OGz and gate GZ were marked. At the beginning of the next column, stages of shift registers RZz, RZZ corresponding to the marked positions are set and shift down performed using the levels from OR-gate OGp10 (which were originally counted) delayed for one column in register Rz as shift pulses. Outputs from the first stages of shift registers RZz, RZZ gate those of the levels which were marked to a line ze to be stored in a circulating register YZ and passed directly and via the register to a line yz to indicate the time position of the character itself within each column.