Patent GB-1143585-A (GB)
IPC: G06K9/78
Abstract: 1,143,585. Character recognition. SOCIETE D'ELECTRONIQUE ET D'AUTOMATISME. 22 March, 1966 [30 March, 1965; 15 March, 1966], No. 12680/66. Heading G4R. Pattern recognition apparatus, for recognising a pattern moving relative to a field of the apparatus, generates at a plurality of channels respective time-varying outputs whose magnitudes are respective functions of the pattern and have an optimum magnitude for respective patterns within the field, the output which approaches the optimum magnitude most closely being registered, the registration being changed if another output approaches the optimum more closely, the output registered being indicated if no fresh registration is necessary during an interval. In a first embodiment (Fig. 1) a document 2 is moved continuously past a window 4, the image of which is passed via a transversely oscillating mirror 5 to a mosaic of photo-cells 12 which feed amplifiers 15. The amplifier gains are preset in response to a reference pattern when further photo-cells 18 detect the absence of the document 2. The amplifier outputs are combined in weighted-resistor circuits 22, one per possible character, which feed means 23 in which the maximum voltage on any input so far is stored on a capacitor and subtracted from each of said inputs (from the resistor-circuits). The subtractors producing outputs set corresponding bi-stables 29 via single-shots 27, the bi-stables 29 being first reset via an OR gate 28 responsive to the subtractor outputs. The OR gate also resets a counter 34 which when it eventually reaches capacity, gates at 31 the bistables to a system output. The counter 34 is driven in accordance with document speed by pulses from a photo-cell 37 and scale 36 lit by a CRT 55 via a slot 35 across which the document advances, feedback of the pulses to control the CRT being provided with adjustment for average light conditions 37, 44, the CRT beam only moving when the document is crossing the slot 35 as detected by two further photo-cells 49. Fig. 5 shows a modification in which to compensate for mispositioning in the direction transverse to document movement, there is provided, besides the oscillating mirror 5, a second mirror 105 positioned by a servomechanism 115 &c., having potentiometer and velocity feedback. When the symbol is projected on to the mosaic of photo-cells, the servomechanism is controlled by a circuit 116 which ORs the photo-cell outputs row by row to feed threshold devices which eliminate the effect of blots. The outputs of the threshold devices relating to the upper and lower halves of the mosaic are supplied in true and inverse form respectively, to a summing amplifier the maxi mum output, so far, of which is stored. If this falls outside a predetermined range, the mirror 105 is moved a predetermined amount in the appropriate direction by two pulses (for movement and braking) supplied to the servomechanism. In addition, preliminary control of the servomechanism is also provided by two devices responsive to the symbols when they pass windows 110, 107 prior to the reading window 4 supplying the mosaic. In the first of these devices, the symbols are projected on to a column of photo-cells 120 transverse to the direction of document movement, the outputs of which are fed to function circuits, each of which subtracts from the sum of a respective photo-cell output and those of the two adjacent photo-cells above, the sum of the outputs of the two photo-cells immediately above this trio and all those below it. The function circuit outputs indicate the position of the lowest line of symbols on the document by the identity of the circuit giving the maximum output. The maximum of all these outputs so far is stored in a capacitor store and subtracted from said outputs, each of the subtractor outputs being ANDed with the inverse of the next lower to feed a coder and ensure that only one input thereof is energized. The multi-bit decoder output, together with a bit equal to " 1 " if at least two adjacent subtractors produce an output, is converted to analogue form to feed the servomechanism. The second device is similar to the first but the light for its photo-cells arrives via the second mirror 105.