Patent GB-850581-A (GB)
Title: Improvements in and relating to electronic reading apparatus
Inventor: BAILEY CHRISTOPHER EDMUND GERV
IPC: G06V10/24
Filed: 1956-03-29
Abstract: 850,581. Automatic character reading. SOLARTRON ELECTRONIC GROUP Ltd. March 25, 1957 [March 29, 1956], No. 10009/56. Class 106 (1). In apparatus for reading and identifying symbols, the latter are scanned twice, the first scan generating a signal which is used to control the second scanning in accordance with the position of the symbol. In Fig. 2, control voltages dependent upon the most westerly and the most southerly parts of the symbols are derived from a system described in Specification 850,582. When the first black pulse is received during a plot scan, a gate 30 is opened and a counter 31 counts the number of scan lines up to a fixed number before initiating in frame generator of the C.R.T. a flyback of predetermined length controlling the westerly positioning of the second scan. A black pulse also unclamps a clamp circuit 35 and applies to a capacitor 38 the negative-going voltage of the line timebase at that instance. The capacitor therefore assumes a charge representative of the most southerly point and this potential biases the line deflection in the second read scan at the completion of which a pulse is applied to a reset generator 40, rendering diode 41 conducting and discharging the capacitor. In a modification the centre of the symbol is located. Fig. 3 shows east to west centring. A scale of two counter 52 is gated at 51 to receive initial plot pulses and counts each line until a black pulse is generated, the latter gating a start/ finish bi-stable device 48. The voltage from 48 controls gates 49, 51 and bi-stable device 50 to stop further counting by counter 52, and removes the inhibiting of gate 54 to allow counter 53 to start counting, but only when there is an absence of black signal along a line i.e. at the east boundary. The outputs of counters 52, 53 are in push-pull connection to a shift amplifier 57, the output of which affects the deflecting means 58 of the C.R.T. 11. The clamp 59 holds the amplifier at zero shift during the plot scan. The north-south centring (Fig. 4, not shown) counts the pulses in each line before a black pulse is received, and the counts are passed to a comparator to ensure that the next line is counted into the counter with the higher count, the final read out being from that with the lower count indicating the number of elements north of the most northerly black element. Similarly the number south of the most southerly black is counted by means of comparators, counters, control gates and bistable devices. The two outputs are combined in push pull (Fig. 6, not shown) by networks of equal resistors and fed to the deflecting coil through the preset variable gain amplifier 57 (Fig. 3). The outputs of the north-south determining circuits may be applied to " or " and "and " circuit elements 87, 88, 89, 90 (Fig. 7) and controlled by a video bi-stable device 91 to count the pulses west and east of the symbol, the output of these counters 92, 93 also being fed to the deflecting coils of the tube. Specification 850,583 also is referred to.