Patent GB-864522-A (GB)
Title: Improvements in character sensing devices
IPC: G06V30/10
Filed: 1957-12-24
Abstract: 864,522. Automatic character reading. INTERNATIONAL BUSINESS MACHINES CORPORATION. Dec. 24, 1957 [Dec. 31, 1956 (2)], No. 40010/57. Class 106 (1). In an automatic character-reading device scanning means sense the character in a plurality of vertical scans and produce signals representing the parts of the character detected at each scan, delay means receiving these signals and giving an output after one scan period, means to compare signals from successive scans giving outputs indicating correspondence or non-correspondence, further delay means receiving and delaying by one scan period the comparator output and a further comparing means comparing the output from the first comparing means with the output of the delay means which delivers a coded representation of the result of the comparison. Card.-As shown in Fig. 44 the card has a right and a left side. The right side, the scan area, carries data to be read arranged in eight horizontal rows between field marks, each of which consists of at least five vertically arranged dots making a line of twice the height of the character to be identified, and equal to the scan length. Characters can be recognized in any of three fields in any one row on a single scan of the row. The left-hand side has 38 columns for punching data read from the selected row of right-hand side. Scanner, Fig. 6.-The card 22 bearing the characters to be read is fed from a hopper and forwarded by rollers 24, 25 to the position shown in Fig. 6 where the leading edge is just gripped by the feed rolls 34, 35. A card lever 96 closes a contact when a card is in position. The character on the underside of the card is illuminated from source 97 and the reflected light passes through lens 98 on a reciprocating rack 99 driven through an electrostatic clutch 105 from motor 104. The rack carries a contact 113 which engages a fixed contact when the rack is in the rest position. The rack moves to scan the proper amount of the card and at the end of its movement it causes contact 115 to transfer from contact 116 to contact 117 to de-energize the clutch. The lens is then returned to its rest position by spring 112. The image of the character is reflected by mirror 118 through lens 119 on to a plate 120 having a slit 121. As the lens and rack move the images of the characters pass vertically over the slit. During this movement slits 124 on disc 122 pass in succession along the slit, the light transmitted passing to a photomultiplier. The photomultiplier therefore sees rapid vertical scans through the character (see Fig. 52a). Disc 122 has a magnetic surface 126 which coacts with reading and writing heads 127 to serve as a store 5, Fig. 1. The scanning lines are shown in Fig. 52a, light reflected from these lines being transmitted to the photomultiplier in block 2, Fig. 1, to give an output which is amplified with a clipping control so that if the photomultiplier output does not exceed a certain level a reference voltage is produced whereas if it does another fixed level is produced. These signals pass to the minimum black-minimum white circuit which consists of a single-shot multivibrator having a time constant such that it produces a thirty-five microsecond output pulse which is used to gate the output from the video amplifier so that when a change of output occurs no more information is passed for thirty-five microseconds. The signals thus pass to a de-fuzzing circuit which eliminates spurious marks as at e, f and g, Fig. 52b. For this purpose the signals derived from each scan are stored in a section of magnetic store 5 and compared with those from the next scan. An output is produced only where the signal is repeated in consecutive scans. Thus the presence of a bit " a " from a prior scan and bit " b " from a present scan gives an output bit " a + b." But spurious marks giving bits " e," " f," " g are eliminated since there was no equivalent bit in the prior scans (on the right). Signature components.-The "defuzzed signals from the present and previous scans are compared in the second comparator to determine what " signature components " are present. The presence or absence of a large number of different shapes, combinations of shapes and shapes in different parts of the character are looked for. Signals are derived representing 32 such " components." For this purpose the defuzzed signals are recorded on the magnetic surface 5 and read off again after a delay of one scan. The black and white signals in a scan are fed to a circuit in which the number of changes from white to black and from black to white are counted and used to set up triggers corresponding to the number of crossovers and included white areas encountered in a scan. The data from the prior scan is read out of store 5 and the number of crossovers and included white areas are found by a similar circuit. By comparing data from prior and present scans it is readily determined whether an included white area is open or closed to the right. For example in the character " 1," Fig. 53a, the present scan S finds an included white area WIs but there is no corresponding white found by the prior scan r, the included white area is therefore seen to be closed on the right (WAI/CR). If a white area Wr found in the prior scan had corresponded with the included white area WIs of the present scan, the included white area would have been open to the right WAI/OR as shown in the top part of character " 5," Fig. 53b. These components are registered on triggers. By further comparisons between present and prior scan data other components are extracted and where included white area components are detected it is determined whether they are open or closed on the left. Where sloping lines are detected it is determined whether they are long or short and whether they slope upwardly to the left and means are provided to detect the existence of left or right overhangs. The size of the black or white areas encountered in a scan is determined by passing sync pulses to counters during the time the scan sees black or white. A vertical line (component VL) may be defined as a black signal lasting for fourteen pulses. This is combined with the component signal indicating three cross-overs to produce a VLL component which means that a vertical line has three cross-overs to the right of it. A long included white component LIW may be extracted by counting the duration of a white signal on a scan, a count of nine sync pulses being sufficient to give this component. All components when they are detected are entered into triggers and the outputs of these triggers are gated together in certain combinations to produce output signals indicating which digit has been recognized. This is effected by plug connections there being, in the case of some digits, two or three alternative gating combinations, which are commoned. The output on the line corresponding to the digit recognized is gated with an " end of character " pulse. This signal is receded in a three-out-of-six code for storage on a magnetic drum. As described above, characters on a card are separated into fields by field marks consisting of five or more dots in a vertical line. These are detected by a circuit which responds to five cross-overs. Storage.-The scanning disc 126 (store 5, Fig. 1) has a magnetizable surface 126 forming a storage drum. This is divided into four quadrants, each quadrant being divided into sixteen positions and each position is divided into three banks each having six storage positions. A card is sensed in the first cycle, positioned in the next and punched in the third cycle. Data from the successive cards is entered in rotation in the three banks, the storage position being cleared when the data is read out to punch the card. The write control (block 9) enters the data recognized into the appropriate bank and the read control 15 reads the appropriate bank and enters the data in a temporary store 16 to be used for setting up the punch magnets. For this purpose the punch 20 generates three-out-of-six code at each cycle time corresponding to the position of the card and this is compared with the coded digit in read register 16. On agreement a thyratron fires to set up the corresponding punch magnet. The data is punched into the card as it advances row by row under the punches the data being entered in the same right to left order as the data printed in the selected row on the right-hand side. Field selection (block 8).-Up to sixteen characters may be sensed in each row printed in up to three out of five fields. The field marks are passed to a counter, connections from which determine whether or not a field shall be sensed and its data recognized. The characters in each field are counted in another counter so that should it be desired, for example, to sense a field which contains ten characters, the counter is plug connected to the machine control so that only the data from this field is punched. A circuit inserts an appropriate number of zeros to the left of the highest significant digit to make up the proper number for that field as determined by plug connections. The field marks limit the area of the recording space. Characters crowded against the field marks on either side are detected, and characters projecting above the upper ends of the field marks or below the lower ends are also detected. Punching of the card from these characters is prevented. Specifications 806,457 and 814,092 are referred to.