Patent GB-932063-A (GB)
Title: Improvements in or relating to character identifying apparatus
IPC: G06V30/10
Filed: 1960-11-14
Abstract: 932,063. Automatic character reading. SIEMENS & HALSKE A.G. Nov. 14, 1960 [Nov. 13, 1959], No. 39087/60. Class 106 (1). In an automatic character reader the character is scanned on a series of vertical lines as shown in Fig. 2 and the " black " and ' white " signals produced in each scan are compared with those produced in the previous scan to detect the presence of angles or cavities such as D and K, these features being used to recognise the character. The signals derived from the scanning are gated with clock pulses so as to sample each vertical scan at a number of instants producing at d, Fig. 13, for each vertical scan of the character, a group of binary signals which are entered serially into a store S consisting of a number of shift registers the output of each being connected with the input of the next and each being adapted to contain a group of signals representing a vertical scan. The number of shift registers is sufficient to contain all scans intersecting a character. The vertical height of the character is determined by a circuit connected to the inputs of each of the shift registers which finds the blank lines above and below the character and enters the number of bits between these lines into the counter L. The signals emerging at e are smoothed by one or more circuits G each of which compares signals from adjacent scans and gates them together to remove irregularities of outline. For this purpose the scan signals are delayed for one scan in a shift register. The smoothed signals f are delayed in a further shift-register R and also applied directly to a gate comparator V which compares successive pairs of signals in adjacent scans. Gates G10, G11 G01 and G00, Fig. 6, respond to these conditions on the input lines n and n-1. When both are ones," i.e. black signals, the store S11 is set to enable gates G1110 and G1101 so that when subsequently a black and a white signal are detected by gates G10 or G01 one of the stores S1110 or S1101 is set. A further double black signal 11 causes the corresponding gate GD or GK to set store SD or SK. The shape element D, Fig. 2, is an angle or cavity open to the right and it is represented by a sequence of signals from adjacent scans 11, 10, 11, i.e. both black, then left-hand black and right-hand white and later, again both black. The element K is opposite. Across the width of the character there may possibly be three such shape elements. The order of their occurrence is important and they are counted in a counter Z, Fig. 13. In this the signals D and K are passed through an Or gate GDK, Fig. 7, and gated with signals O and U from the counter L which indicate that the scan is in the top or bottom half of the character. Successive angle signals D and K are therefore counted in counters Zo or Zu depending upon whether they occur in the top or bottom halves of the character. The outputs 1, 2, 3, 1<SP>1</SP>, 2<SP>1</SP>, 3<SP>1</SP> of these counters are gated in circuit F with the successive (up to three) D or K signals and the top and bottom half signals o, u, as shown in Fig. 8. The triggers SKlo &c. represent respectively that the first angle in the top half was open towards the left (K) and so on, outputs being provided on terminals K1o &c. if these shape elements have been detected. Altogether there are ten output lines making provision for a first, second and third angle, either D or K, in the top half and a first and second angle, either D or K, in the bottom half. These outputs are gated in appropriate combinations in the recognition circuit to produce signals on character leads. Numeral " 9 " for example is distinguished by a first D angle or cavity in the top half, a second K angle or cavity in the top half and a first K angle or cavity in the bottom half. Stroke detector To facilitate recognition of other characters, e.g. " 1 " or ' 4 ", a vertical stroke detector circuit E, Fig. 13, is provided into which is entered a number representing the number of bits in a scan of seven-tenths of the height of the character. The double black output 11 from the adjacent scan comparator, Fig. 6, is applied to step this number down towards zero, each successive 11 signal subtracting one. A zero signal indicates that two adjacent scans were black (11) for at least seven-tenths of the character height and an output is produced which is gated with the output of a trigger set by either a D or a K signal. The result is stored on two triggers to give outputs Sl or Sr signifying that a stroke has been detected and it occurs before or after, respectively, an angle or cavity. Timing and reset pulse lines are shown dotted in Fig. 13.