GB1015886A - Improvements relating to character recognition systems - Google Patents

Abstract

1,015,886. Character recognition. FERRANTI Ltd. May 22, 1964 [May 24, 1963], No. 20727/63. Heading G4R. A character is scanned in two angularlyspaced directions by lines of light 13 (Fig. 2) moving in the direction 14 from cathode-ray tubes 11 or 111 (Fig. 1) and the resultant waveform produced by a photo-cell 15 is modified by removal of the D.C. component by a capacitor 17 and addition of a fixed D.C. by a restorer 21 and the modified signal is applied to a delay line 25 for comparison with a standard signal with mean amplitude determined by an integrator 23 from a pulse generator 27 applied through a selector switch 31 to one of coils 26 on the delay line 25 such that coincidence of signals at 34 gives a signal at 37 if they are the same. The modified signal is applied to an amplitude discriminator which produces a time pulse just outlasting the scan period to activate the pulse generator 27 at the end of a pulse and also a comparator 36 which compares the root-mean-square of the summated signals at 34 and the integrated signal from 23. Signals on lines 37 and 137 (Fig. 4) from the two directions of scanning indicate an identity through an " and " gate 40 connected to a rotary switch 41 moving in synchronism with switch 31. An equality signal on only one line 37, 137 gives a warning output on line 46. The coils 26 are wound one on top of each other or side-byside with a delay in the pulse circuit inverse to its distance from the pick-up 34 or on a number of equal length branch lines from the central delay line 25. Instead of equalizing the mean amplitude of the standard signals, the integrated signal is applied as a gain-control to a variable gain stage following the D.C. restoration stage 21 such that the modified signal is given a constant predetermined mean amplitude and the second input to the comparator 36 may be supplied from a fixed potential source. The standard waveform may be produced on an amplitude sampling basis in which pulses are applied simultaneously to identical coils set up along the delay line 25 and connected through a matrix of resistors arranged to produce currents with amplitude corresponding to the standard character.