Patent GB-981500-A (GB)
Title: Pattern identification apparatus and methods
IPC: G06V30/168
Filed: 1963-05-20
Abstract: 981, 500. Automatic character reading. INTERNATIONAL BUSINESS MACHINES CORPORATION. May 20, 1963 [May 21, 1962], No. 19944/63. Heading G4R. In a character reading apparatus a signal is derived from the signals obtained by scanning the character by accepting all portions having a magnitude greater than a predetermined value and also those portions having a magnitude below this value when they are needed to ensure that the output signal defines a continuous line pattern. The signal derived by scanning a character by means of a flying-spot scanner may be shown as in Fig. 2A, the number representing the magnitudes of the original produced at each sample point. To eliminate all signals below 2 would discard necessary data and leave an incomplete pattern. The invention retains data where it is necessary to provide a continuous pattern line and discards superfluous data on each side of the line. The pattern obtained is shown in Fig. 2B. A decision as to whether any particular point is necessary is made in logical circuits controlled by the presence or absence of signals in the surrounding points. A matrix of nine points is considered as shown in Fig. 4A, the unknown point X being in the middle. Point X, if absent, is taken as being present if it is required to connect other points, say A and C, which would otherwise not be connected, because the signal in the B position is absent as the result of a previous operation of this stage. Some of the logical conditions which necessitate a signal to be present at X are shown in Fig. 4A. The circuit is shown in Figs. 5A, 5B, 5C. The character is scanned by a flying spot from C.R.T. 6 and photo-cell 7 provides corresponding signals for application to a gated amplifier 15 in which they are sampled by pulses synchronized with the scan of the C.R.T. 5. The samples, corresponding to successive points on a co-ordinate array as shown in Figs. 2A, are applied to a threshold device T1 with a low level e.g. about 0. 5 where the signal varies from 0 to 3. A series of "1's" are accordingly entered, in vertical scans, into a shift register 19 and outputs are taken from positions so spaced that they correspond to the points A, B, C, D, E, F, G and H in Fig. 4A. The shift register must contain simultaneously the data relating to three vertical scans, with say 20 sample points in each. The outputs are applied to connectivity function circuit 37 along with outputs from the next shift register 21 which stores decisions made on previous points in the circuit 37. The output of circuit 37 which indicates whether X is to be taken as "1" because it is necessary for line continuity or "0" because it is not, is applied to an OR gate 39. The other two inputs indicate the "blackness" range of the point X which has been suitably delayed at 41 and applied to threshold circuits 43, 45 "T 1 -low" and "T 1 -high". These may be set at values say ¢ and 1¢. The output of circuit 43 is inverted at 44 so that, between them, these two circuits provide a signal for OR gate 39 if the magnitude of the signal for point X is below or above the magnitude range for which the first stage is set. In these two cases of if the point X is required for line continuity the gated amplifier 49 is enabled to pass the corresponding magnitude signal to the next stage. The input to the next shift register is through a higher-level threshold device 17 and other circuitry as the same as in the first stage. Signals are passed on to the Nth stage and so on, lower magnitude signals being successively eliminated unless they are required for connection purposes so that the final signals represent the array of dots as in Fig. 2B. The connectivity function circuits consist of combinations of inverters and gates. In addition there is an adding and threshold circuit which provides an output for the X position if signals are present at more than a certain number (e.g. 6) of the surrounding positions.