Improvements in record reading devices

摘要

873,748. Automatic character reading. INTERNATIONAL BUSINESS MACHINE CORPORATION. April 28, 1958 [April 26, 1957], No. 13384/58. Class 106 (1). A character recognition device comprises record scanning means producing a series of differentially timed signals and processing means translating these signals into a series of signals representing by their amplitudes the shape of the right or left-hand contours of the character. A character written on a sheet 3 is scanned in a raster pattern by a cathode-ray tube 1, the reflected light being received by a photo-cell 4 to produce a train of signals. These are amplified at 5, inverted at 8 to derive negative pulses and passed to a driver 9. When the scanning beam meets the left-hand side of the character driver 9 emits a positive pulse which is applied to trigger 11, 12 to cause valve 11 to conduct and the fall in plate potential is used to cut-off valve 8 to block further pulses until the trigger is reset by differentiated line flyback pulses of the oscillator governing the deflection of the scanning beam. Valve 8 is therefore blocked until the next line and only the first pulse, corresponding to the white on the left of the character is applied to the subsequent circuitry. Positive signals from valve 9 are also applied to a clipping circuit comprising condenser 13, resistors 14, 15 and diode 16. The saw-tooth deflection voltage is applied to diode 16 and clips the applied pulse to a voltage depending on the time of occurrence in the scan. These clipped pulses 17 are applied through diode 18 to a point 19. Negative pulses from inverter 10 are also passed via a similar clipping circuit comprising condenser 23, resistors 24, 25 and diode 26, through diode 28 to point 19. At point 19 therefore, there occurs a series of complementary positive and negative signals the amplitudes of which represent the contour on the left side of the character at successive levels. This signal sequence is integrated in condenser 29 and differentiated in the units 20, 21 to provide signals representing the left-hand contour. A line from the differentiator is connected to an identification device, not described. The signals relating to the righthand side of the character are processed in a similar way in block 30 except that where two pulses occur in one sensing scan due to double lines the second is used to derive signals for further processing. Double lines.-Characters having double strokes or enclosed spaces are detected by a circuit having a double grid valve, the signal pulse being applied directly, to one grid and through a delay line to the other. If a single pulse is applied it has already died away on the lower grid before it reaches the upper grid through the delay and the valve does not conduct. A second pulse arriving shortly after the first coincides with the delayed first pulse and the valve conducts. A further circuit for detecting double pulses is also described.