Patent GB-825597-A (GB)
Title: Character recognition equipment
IPC: G06V30/20
Filed: 1958-04-11
Abstract: 825,597. Automatic character recognition. STANDARD TELEPHONES & CABLES Ltd. April 11, 1958 [April 17, 1957], No. 11514/58. Class 106 (1). To recognize characters they are first electrically simulated in a plane field of current flow or potential by scanning them raster-fashion by one or more photocells, assigning to each elemental area one point of the field of flow or potential and impressing a potential on those points of which the corresponding elemental areas have more than a predetermined blackening. The area containing the character is divided into elemental areas b(x,y), Fig. 1, each of which has a photo-cell to provide through an amplifier and, if necessary, a store, a voltage Uo when, say, more than 50% of the area is blackened. This may alternatively be effected by using a column of photo-cells to scan over the character area or a single cell scanning the area in a raster pattern. The field of flow consists of a network of resistors R, Fig. 2, the junctions P(x,y) being the points to which the potentials from the amplifier are applied through diodes Di, Fig. 6. The marginal points may be shortcircuited and earthed. The currents I(x,y) which flow into the points in order to maintain the potential could be used to recognize the characters. Alternatively the potential distribution could be used. If a zero potential were impressed on those points corresponding to non-blackened areas, either the currents required or the resulting potential distribution could be used to recognize the character. The current density flowing into a blackened point depends upon its relationship with other blackened points and is the greater the more this point projects into a non-blackened field. This current may be roughly classified into five stages from " 0 " (where there is almost no current owing to the point being strongly screened by other blackened points) to " 4 " (where there is a very strong current at a freely disposed end point). Examples of points of each stage are shown in figures in Fig. 3. The character can be recognized by studying the distribution of different areas of current density. This is effected by scanning or sampling the potential field horizontally on three tracks as shown in Fig. 5. There is an upper, a middle and a lower track and the current densities at the scanned points is used to determine whether one or more of three shape elements are present in each track. These are shown in Fig. 4, a shape L (open to the left), shape R (open to the right) and a closed shape G, each producing a different potential distribution along the scanning line. The potential distribution is investigated by comparing the potentials at three adjacent points successively along each scanning line. For this purpose the spaced contacts of three rotary switches or their equivalents DR1, DR2, DR3, Fig. 6, are connected to the points P(1,y), P(2,y), P(3,y) &c. of the scan line in the field of flow. The switches rotate together and present to comparison circuits the potentials at three consecutive points advancing along the scan line. The three consecutive points are simultaneously compared with other on each scanning track to derive signals indicating the presence of L or R shapes. The G shape is detected by comparing the potential U<SP>1</SP>x at the amplifier terminal relating to each photocell of the raster with the potential Ux at the corresponding point on the potential field. These potentials are simultaneously presented by switches DR2 and DR4 and the comparison circuit emits a signal indicating the presence of a G shape if the necessary conditions are satisfied. Within the closed ring all points have the maximum potential but no potential is actually applied from the photo-cell amplifiers because the area is white. L, R and G shape signals are stored in triggers and converted in a network of gates to produce signals on the line appropriate to the character recognized. Specification 825,598 is referred to.