Patent GB-1033531-A (GB)
Title: Improvements in and relating to character or the like scanning apparatus
IPC: G06V30/146
Filed: 1963-01-15
Abstract: 1,033,531. Automatic character reading. PHILCO CORPORATION. Jan. 15, 1963 [Jan. 15, 1962], No. 1765/63. Heading G4R. In apparatus for reading characters arranged in rows, a timed signal is produced which indicates the relative position of the character in the scan area, there being means for generating a reference timed signal, comparing means and means for displacing the scan according to the difference in the timing of the two signals. The characters are scanned in turn each by an area swept by a vertical raster by a spot from CRT 40. The vertical strokes may be of constant velocity or the scanning spot may move in a series of steps. Reflected light is received in photo-cell 46 to generate signals which are clipped and sampled at 52 to give a train of " black " or " white " signals for each vertical scan. These binary signals are entered into a shift register matrix 56, combinations of the units of which are connected to circuits 80, 82 &c. designed to recognise particular patterns. The recognition circuits recognise the character when it is properly located in the matrix. Since the stages are connected serially the pattern enters from one side and moves across the matrix, circulating vertically between each horizontal step in the same manner as the moving spot of light scans the character. When the whole character is entered in the matrix, at some point in a vertical circulation the recognition circuit corresponding to the character sensed responds with an identifying signal. The outputs of all recognition circuits are connected to an Or gate 84, the output 86 of which is therefore a timed signal occurring at the instant of recognition. If the character sensed is located high in the scanning area the recognition signal will arrive late. If the character is low it will arrive early. Counter 124, Fig. 2 (not shown), counts pulses representing the twenty-two steps of the vertical scan. At fly-back time a signal is produced on line 96. The count is converted by resistors 128a to 128e into a staircase voltage for the vertical scan. For correct registry the recognition signal arrives at the same time as the flyback signal on line 96. A gate 95 blocked by this signal allows the recognition pulse to pass to counter 110 if it occurs earlier or later than the fly-back signal. Controls 96 and 98 from counter 124 set the counter 110 to count up or down according as to whether the recognition pulse is earlier or later than the fly-back. Counter 110 is connected to resistors 112a to 112d to give a variable bias voltage which is added at 120 to an initial position voltage from source 118. The addition is added at 122 to the vertical staircase voltage. The arrangement is such that if displacement of a character is detected, the scan area is shifted up or down one increment for the next character of the line. As a result the scan area may follow the characters in a sloping line, Fig. 5 (not shown). If only one character in a line is displaced the following scanning frame is correspondingly displaced, Fig. 6 (not shown). Delays may be introduced to avoid this. In another form, the staircase vertical scan voltage is compared with a reference level and the difference at the occurrence of a timed pulse representing the character position is used to move the scanning area to a centred position over the character.