Patent GB-990531-A (GB)
Title: Specimen identification methods and apparatus
IPC: G06V10/20
Filed: 1962-05-30
Abstract: 990,531. Automatic character reading. INTERNATIONAL BUSINESS MACHINES CORPORATION. May 30, 1962 [June 19, 1961], No. 20754/62. Heading G4R. In a character reading apparatus the character is scanned to derive signals representing black and white areas of the character, some or all of these signals being autocorrelated to provide a multiplicity of second signals representing at least parts of different autocorrelation orders of the character pattern and means are provided for identifying the scanned character from the second signals. A first order autocorrelation function gives the number of pairs of black areas separated by a given distance in a given direction over all possible distances and directions. The function is derived by comparing pairs of points having the same positional relationship all over the character pattern and counting all pairs where both are black. The counts may be tabulated for each positional relationship. A second order autocorrelation function comparisons are made between groups of three points and counting all triples where all three are black. The process may be repeated for any number of points in a group and the general case is considered of autocorrelation functions of first, second, and so on up to the nth order. The character 1, Fig. 1, is scanned in a horizontal raster by a C.R.T. 5 and the reflected light, received in photo-cell 7, provides signals f(t) representing the character as shown in Fig. 5. Since the speed of scanning is uniform the character may be considered as being represented by a series of fortyfive pulses i.e. a function of time. The f(t) signals are combined in pairs, triples &c. in an N-tuple generator 9 and the outputs applied to identification circuit 11. The N-tuples are extracted as shown in Figs. 28a, 28b, 28c, the photo-cell output being sampled at 45 points in the scan, to obtain the series shown in Fig. 5, and applied to a shift register 125. At each step the signals in the register stages are gated, in gates 127, with the incoming signal. This compares each position in the signal with each other position and black-black coincidences appear as output pulses which are counted by being integrated in integrators 151. The output from the 2-element combination gates are applied to further gates 129 also connected to stages of the shift-register, thereby obtaining 3- element combinations and so on. The coincidences are counted as before. The integrator outputs are D.C. voltages each representing a term in the first, second, --nth order autocorrelation functions. The first and second order functions are shown in Fig. 9 for the character "3". The first order terms are indicated along the bottom edge and again on the diagonal. Only half the table is shown since the other side is a mirror-image. The values in the table indicate the number of coincidences of the original signal train with both of points t 1  and t 2  which vary from 0 to 22. Shaded areas are points which are on the fringe of the pattern area and can be ignored. The integrator outputs after amplification at 153 are applied via resistors to certain ones of character leads SSR1-SSR0. The connections are designed so that an ideal character gives a maximum output on the corresponding lead. The lead signals are normalised for area of character by weighted resistors 157 and applied to a transistor circuit which determines the most positive signal. In this circuit each lead is connected to an N-P-N transistor with a common emitter lead. Current flows only in the transistor connected to the highest signal. The conducting transistor operates a relay and lights a lamp. In the form of Fig. 3 the integrator outputs are applied to circuits which derive "entropy" functions E1, E2, E3 (Fig. 9) which represent the "order" or "disorder" of the pattern sensed. The functions are represented by D.C. voltages and are applied through suitably weighted resistors to the character leads as before. In another form certain combinations only of the character positions are compared. These combinations may represent certain shape elements, e.g. a horizontal line. The combinations are stored on flip-flops and the outputs gated to identify the character. In another arrangement successive shape elements operate successive flipflops in recognition chains, one for each character. The first chain to be fully operated identifies the character. Seven shape elements may be specified by the combinations selected e.g. those shown in Fig. 34a. In a last embodiment the shape element signals are sampled at six instants during the scanning starting with the occurrence of the first shape element. The expected occurrences of the shape elements for the ten characters 0-9 is shown in Fig. 34c. The same pattern derived from the scanned character is entered with seven shiftregisters in similar form and gates are provided which compare particular pairs of positions in the same and different columns as the pattern is entered. Coincidences are added in an integrator and the voltages derived are compared after normalisation to obtain the highest. This identifies the character as before. Specification 982,989 is referred to.