Patent GB-986956-A (GB)
Title: Improvements in or relating to character recognition apparatus
IPC: G06V30/194
Filed: 1963-10-16
Abstract: 986,956. Automatic character reading. INTERNATIONAL BUSINESS MACHINES CORPORATION. Oct. 16, 1963 [Oct. 30, 1962), No. 40745/63. Heading G4R. In a character reader signals representing the character or a function of it are compared with a non-adaptively stored set of reference signals and with an adaptively stored set of reference signals, an indication being generated of the most similar reference and altering the adaptively stored reference to bring it into closer agreement with the character. If the font changes or degraded characters are encountered they may still be recognised by comparison with the non-adaptively stored references and the adaptively stored references will be changed into closer and closer agreement with the new font or degraded characters so as to obtain from the adaptively store references a more certain recognition than would be obtained from the non-adaptively stored references. The amount of alteration given to the adaptive references to bring them into agreement with the character sensed depends upon the probability that the recognition is correct and the amount of deviation between the character and the reference. The character is scanned by a flying spot scanner and the signals are entered into two shift registers and recirculated for comparison of each bit position, the pattern in one being shifted after each recirculation into all positions relative to the pattern in the other. During each circulation the patterns are compared by being gated together and applied to a counter which provides a series of counts representing the extent of overlap in each position of displacement of the character relative to itself. These counts are the autocorrelation function of the character and are applied in succession from the generator 11 Fig. 1 to multipliers 15 where they compared with stored values from the fixed reference stores 12 and the adaptive reference stores 13. The products of each term with the corresponding values from the stores are entered in accumulators 17 and the sums normalised so that the largest represents the character sensed. The maximum signal indicator 19 gives a signal e.g. on the "2" lead to indicate that the best match has been with the "2" references in the stores 12 or 13 either the fixed or adaptive. The output, a signal on one of a number of leads, conditions the appropriate one of gates 23 to pass the data from the corresponding adaptive register through Or gate 25 to subtractor 27 which also receives the equivalent data from a register 21 holding the autocorrelation pattern from the generator 11. The differences between the generated and stored patterns is applied to divider 31 where it is divided by the correction factor 2, 4 or 8 by shifting through 1, 2 or 3 stages. The resulting signals are passed through one of the And gates 33 enabled by the recognition signal and used to alter the contents of the corresponding adaptive store 13. Only a portion of the deviation is used to affect the alteration so that no substantial alteration will be made due to erratic or wrongly indentified characters. Where a change of font takes place the contents of stores 13 are cumulatively modified so that the references stored become those relating to the new font. The functions used as a basis for recognition may be derivatives of the autocorrelation functions. For example the autocorrelation functions may be modified by "discriminating functions" which emphasize small differences such as that be - tween "O" and "Q" or by "smoothing functions" which ignore such differences to overcome effects of serifs or noise. As a discriminating function the normalised "second-difference" function may be used, the autocorrelation functions being normalised, so that they are comparable, and then multiplied point by point by a second difference operation. The results obtained for rudimentary characters "1", "2" and "3" are shown in Fig. 28. An error circuit connected to the highest signal detector rejects the character if the ratio between the highest and next highest signals is too low and if the recognitions on the basis of the fixed and adaptive references give different results.