Patent GB-909942-A (GB)
Title: Character reading apparatus
IPC: G06V30/224
Filed: 1960-10-11
Abstract: 909,942. Automatic character reading. NATIONAL CASH REGISTER CO. Oct. 11, 1960 [Dec. 23, 1959], No. 34777/60. Class 106 (1). An apparatus for reading rows of specially shaped characters on a moving tape 12, Fig. 1, has a scanning cylinder 20 having pairs of apertures 22b, 22t which scan the characters on a series of parallel lines horizontal with respect to the character, counters for defining the progress of the scan along the row and further means for each character for counting the number of scans that have intersected the character, means for each character to indicate that scanning has progressed to a point where the two apertures are properly aligned with the upper and lower portions of the character and means controlled by this indication to read out a signal representative of the character. The characters are printed in rows of eight, Fig. 2, each occupying a column, there being at the beginning of each row a printed reference mark 46. The characters are formed as shown in Fig. 6 so as to have vertical parts in certain ones of five vertical strips in both the top and bottom sections. The scanning apertures 22t, 22b cut these parts and each produce five binary digits Tc, Bc as shown in Fig. 6. An image of the character in the sensing station 17 is projected by lens 28 through the window 23 in a shroud 24 on to the cylinder 20. A pair of light-conducting rods 26t, 26b pass light signals appearing through the apertures 22t, 22b to photo-cells 30t, 30b. Peak detectors 32 differentiate the photo-cell signals and produce centrally positioned pulses as shown in Fig. 6. Spurious signals are avoided by using apertures 22t, 22b large compared with the size of such specks as may be present on the tape. Timing pulses are derived from a magnetic track 33 on a disc 36 rotating with the scanning cylinder 20. From the read head the pulses pass via a clock setting circuit 60 and an And gate 66 to the sub column counter 68. Eighteen pulses are counted by this counter during the time taken for the apertures 22t, 22b to cross the width of a column containing a character as shown in Fig. 3. The counter has outputs P1, PU, PV, PW, PX, PY, P17 and P18. The outputs PU-PY each correspond to one of the five vertical strips of the character and each comprise three clock pulses. The outputs P1, P17 and P18 are for setting and resetting purposes. During the scanning of a row the reference mark 46 is encountered first to produce a signal TR. This is used to delay the clock signals in the variable delay core circuit 60 so that the leading edge of the signal TR coincides with the leading edge of the first clock signal C. The core circuit 60 which is the subject of Specification 907,492 is initially set through And gate 70 by a signal TR and a signal KR from the column counter 80. The initial state of the counter 80 is represented by a signal on terminal KS this corresponds to the period during which the scanning apertures 22t, 22b are behind the shroud 24. The counter state KR extends from the time the apertures cuts the area of the window 23 up to the beginning of the first column K1 Fig. 3. The signal TS produced as the scanning apertures emerge from behind the shroud 24 into the window 23 is gated with signal KS in gate 84, Fig. 1, to advance the counter to state KR. When the reference mark 46 is sensed a signal TR is obtained which is gated with signal KR to flip-flop G1; the output starts the operation of the setting circuit 60 so that clock pulses can now enter the counter 68. The previous signal TS is gated with the counter signal KS in gate 94 to reset the subcolumn counter 68 to a count of thirteen corresponding to the centre line of the reference mark 46 in Fig. 3. The first five clock pulses therefore advance the counter 68 to eighteen so that it resets and begins counting from zero at the beginning of the first column K1 The reset pulse advances column counter 80 to state K1. As the apertures move across the tape the counter 68 counts up to eighteen as each column is traversed and counter 80 advances successively to K8. During the first scan which is represented by the line 88 for the top aperture 22t and line 89 for the bottom aperture 22b, the top aperture passes through column K1 without intersecting the first character " 2." No signals therefore appear on the output line T. The next character " 4 " is vertically out of alignment and is intersected twice by the line 88. A signal TC is produced and used to set a " blackpresent " trigger A1, which is reset at the end of the column by signal P17 from counter 68. The output of this trigger is gated with the P17 signal to start a scan counter 100, subsequent scans being counted automatically. The first scan to cut a character is counted as scan S 1 for this column. At the eighteenth pulse P18 the reading of the counter 100 is entered into a core store 104 which has four cores for storing a count in binary scale for each column. At the beginning of each column, at P1 time, the count for that column is read out of store 104 and reentered into four triggers of counter 100. The counter 100 consists of triggers and cores coacting as described in Specification 878,870. Vertical out-of-alignment is compensated for by taking for each column the first scan to cut the character as the first scan and the signals derived from the fourth scan are taken for recognition of character. As shown in Fig. 3 these are different scans for the two characters. During the third scan for any column, the flipflop F1 is set by a P17 signal and an S2 signal through gate 112. The signal P17 also advances the scan counter to S3. The flip-flop F1 when set indicates that the next scan will be the " read " scan (see Fig. 3). The set condition of this flip-flop is stored in the store 104 and during the next scan of that column the flipflop F1 is set again by the signals in store and opens gates 124, 126 so that the top and bottom signals Tc, Bc pass to storage elements 120, 122 being distributed by signals successively on leads PU, PV, PW, PX and PY. Since all characters have a part in at least either the top of bottom portions of the U zone. To compensate for horizontal misregistration, these signals Tc, Bc are used to set flip-flop G1 through Or gate 132 and And gate 134 opened by the " read " flipflop F1. The phase of the clock pulses is set by the variable delay core circuit 60 to coincide with either signal Tc or Bc whichever is present. This signal is also used to set the counter 68 to count P3, that is the centre line of the U zone. The character is thereby synchronized with the clock pulses and with the counter G1 irrespective of whether or not the character is accurately positioned with respect to the reference mark 46. After the read scan the stores 120, 122 contain binary bits corresponding to the top and bottom scans and at time P17 the scan counter advances to count S4. The signals from the elements of the storage elements are applied to a decoding circuit 142 which at time P18 in the fourth scan S4 converts them to a representation on one of a number of character leads. The outputs may be gated with the column counter outputs K1-K8 and distributed to visual indicators 103. Specification 909,943 also is referred to.