Patent GB-1028881-A (GB)
Title: Character recognition apparatus
IPC: G06V30/224
Filed: 1964-01-09
Abstract: 1,028,881. Automatic character reading. NATIONAL CASH REGISTER CO. Jan. 9 1964 [Feb. 8, 1963], No. 1032/64. Heading G4R. In a character recognition apparatus the character is scanned by first scanning devices along one or more parallel paths to obtain signals from which it is recognized and there are also a plurality of second sensing devices scanning the character on a number of parallel paths providing signals which pass to registration circuitry providing a registration signal which is used to connect one or more of the first scanning devices to the recognition circuitry. The characters are specially shaped so as to have parts lying in five vertical strips and recognition is made on signals representing the disposition of parts in the upper and lower halves of the character. The characters are arranged in rows of eleven across a tape, Fig. 2 (not shown), characters being sometimes misaligned, defective and badly spaced. The tape is fed through the scanner, Fig. 3 (not shown), which has a curved guide 41 with a slot 54 through which a row of characters is exposed. The exposed part of the tape is illuminated by lamps 42 and the image reflected by rotating mirror 43, through lens 44 and half-silvered mirror 46 to photo-cell units 47, 47<1>. Each unit has two lines of apertures and the arrangement is such that relative to the projected image the lines of apertures interlace as shown, Fig. 6 (not shown). Each aperture is connected by way of a light guide to a photo-cell. The register apertures a0-a15 sense the character first and a signal is derived which is used to select those two of the reading apertures r1-r17 which scan through the upper and lower halves of the character. The outputs of all the photo-cells are amplified in amplifiers the sensitivity of which is controlled to compensate for brightness of background by a background signal derived through sensing aperture Sel. Mounted on the guide 41 is a white strip 56 which is sensed by aperture h1 and below this is a row of clock marks 55<1> sensed by aperture c1 The signals A0-A15 from the registration cells, after amplification are applied to set corresponding flip-flops C0-C15, Fig. 7 (not shown), and the outputs are gated to produce a marking on one of twelve leads St1-St12. This signal is converted to a combination of markings on one of four leads and stored on four flip-flops D1-D4. The signal is reconverted to a marking on one of twelve leads and applied to relay circuit 89 which produces corresponding selecting signals T1-T12 and B5-B17 for gating network 90. The reading cell signals R1-R17 are applied to network 90 and the selected signals representing the top and bottom parts of the character appear at t and b. These are amplified and clipped. Clock pulses from the marks 55<1> are applied to a frequency multiplier which is controllable to adjust the frequency of the output clock pulses to be appropriate to the large or small font. The clock pulses are applied to a gate which opens as soon as the first black signal T or B appears allowing the pulses to pass to a counter having a scale of twenty-five. The first fifteen provide corresponding outputs and these are combined to give outputs successively on five leads PU-PY, Fig. 12 (not shown), corresponding to the five column positions of the characters. The corresponding character signals are gated into ten flip-flops G1-G10. Circuit 166 receives the combination of signals stored in the flip-flops G1-G10 and recognises the character from this combination. If the combination is not one which represents any of the possible characters, an error signal is produced. The character is identified by signals on four leads V1-V4 and they are entered into a flip-flop store VBS under the control of signals K1-K11 representing the eleven characters in a row. During movement of the row of characters through the sensing station six scans are made of each character during which recognition could take place. No output appears on leads V1-V4 until an acceptable combination of ten signals is received. As each character in the row produces an acceptable (or correct) combintaion a signal is produced on lead Vc to set a corresponding one of eleven triggers Va5- Vk5. If the row is correctly read in the first scan all these triggers are set and the recognition signals are entered into the store VB5. The output signals of triggers Va5-Vk5 then inhibit gates 194 to prevent subsequent recognition signals being entered into the store VBS. If some characters do not produce correct combinations in the first scan, the signals produced in the second scan may give recognition signals which are entered in the corresponding columns of VBS. At the end of six scans each character should have produced valid recognition signals and the stored signals are read out, the store being reset in readiness for the next row. However, if, at the end of six scans the triggers Va5-Vk5 are not all set the apparatus is stopped. In a modification the store VBS is a core store and the recognition signals entered are compared in subsequent scans with new recognition signals from circuit 166. If the same recognition signals appear in two scans they are accepted. If the stored signals do not compare they are rejected and the last valid recognition signals are accepted. Successive scans relate to successive apertures down the lines a0-a15 and r1-r17. The amplifiers associated with these photo-cells have graded sensitivities so that in successive scans the sensing is less sensitive. This may allow spurious marks to become ignored so that later scans are more likely to produce a correct recognition. The conditions under which signals are accepted as correct may be successively relaxed in other ways.