Patent GB-1138453-A (GB)
Title: Character recognition system
IPC: G06V30/144
Filed: 1966-03-18
Abstract: 1,138,453. Character recognition. FUJITSU Ltd. 18 March, 1966 [18 March, 1965], No. 12168/66. Heading G4R. In a character scanner, the scanner executes a loop-shaped path wider than the character line and follows the line under control of a linedirection signal obtained from scanner output signal magnitudes proportional to the time lapses between loop beginning and crossing the line. A character formed of straight lines and arcs of circles is optically projected on to a planar array of photo-electric elements which are scanned for read-out by an electron beam. Sawtooth or sine voltages are used to control the electron beam to locate the character then sine and cosine voltages are used to produce a circle of diameter greater than the character line width which is stepped along the character as follows. The scanner output 108 (Fig. 5) is differentiated 201 and rectified 202 to produce pulses whose time positions represent the times of crossing the character line boundary. These pulses (four per circle of the scan) are used via a shift register 203 and differentiators 204 to sample at 205 a ramp voltage produced at G for each scan circle. The average of the samples is obtained by transistors 208 and resistors 209 and fed to recognition means from 106 and to a difference amplifier 210. The amplifier subtracts the ramp voltage corresponding to 90 degrees of the scan circle and sampled from the ramp at 219 by the pulse d which triggered the ramp delayed at 218. The amplifier 210 output which represents the direction of the character line is used to remove the top of the ramp voltage at 211, producing a duration-significant pulse which is differentiated 212, 213 to produce a positive and a negative pulse which are used to sample the sine and cosine voltages respectively at 214S, 214C, the samples being applied via terminals 109, 110 to step the scan circle along the character line. This stepping occurs in alternate cycles of the sine and cosine voltages, the scan circle being produced in the other cycles, a flip-flop X controlling this alternation. When one end of the character has been reached, the character is followed back to the other end. The voltage waveform fed to the recognition means from 106 has flat portions (of different amplitudes) for the straight character lines and ramp portions for the arcs of the character. For recognition purposes, the amplitudes of the flat portions are digitized after subtraction of the amplitude at the beginning of the waveform, and the ramps are differentiated and the result digitized. Rotational displacement of the character (including the character being upside down) will merely increase the amplitude of all parts of the waveform equally and so not affect the recognition. The diameter of the scanning circle may be reduced to avoid ink blots. The diameter is increased each time an interruption of the character is encountered to distinguish this from line end. The character following time may be measured for checking purposes. The circle centre may be centred on the character line width using an auxiliary signal. The scan circle may be replaced by an oval or octagon.