Patent GB-917574-A (GB)
Title: Improvements in or relating to automatic reading apparatus
Inventor: HATLEY DEREK JOHN
IPC: G06V10/10
Filed: 1960-11-25
Abstract: 917,574. Automatic character reading. SOLARTRON ELECTRONIC GROUP Ltd. Nov. 17, 1961 [Nov. 25, 1960], No. 40673/60. Class 106 (1). . In an automatic character reader of the kind in which the character  is scanned to produce signals and reconstituted as a pattern of stored " black " and " white " signals in an array of storage elements interconnected to form shift registers through which the pattern is progressively vertically shifted, means are connected to a row of the elements to detect " black " signals therein at each shift from which the boundary of the true pattern is determined and subsequently brought to a predetermined position in the array. The characters are printed in rows across a paper tape 20, Fig. 4, which is continuously fed for example as in Specification 907,970. The characters are printed by a type wheel of a kind liable to make spurious marks above and below the character 17, 16, Fig. 2, but not at the sides, i.e. between the characters. The apparatus is designed to eliminate the marks 16, 17. A cathoderay tube 23 makes a vertical raster over a sensing area 18<SP>1</SP>. The flying spot is focused through a half mirror 22a on to the paper 20 and the reflected light is received by a photo-cell 25. Light transmitted through the half-mirror is received in a photo-cell 25a and used to keep the brightness constant by a feed-back through amplifiers 26a. Over each area 18<SP>1</SP> there are two scans of 14 and 28 strokes respectively and a switch 26 passes the signals from the first to a contrast control circuit 27 and the second to an amplifier 28. The circuit 27 produces from the first scan a clipping level for a clipper 29 to which the amplified second scan signals are applied. For this purpose the circuit 27 may detect the peak black and peak white signals and take the mean. Alternatively, it may integrate the black and white signals. When the second scan is clipped at this level some of the spurious signals resulting from discolourations in the paper are eliminated. The resulting binary signals representing the 28 strokes of the second scan (covering area 18<SP>1</SP>, Fig. 2) are sampled in quantizer 29a and then distributed by gates 30 to the successive columns of the storage array 32. The signals from the successive strokes are repeatedly entered into the first column of the array 32 until the first black signals are detected. Subsequent strokes then pass to successive columns, the distributer 31 opening the gates 30 in turn. The character size is such that it should be easily covered by fifteen strokes, i.e. area 18, and it is stored as shown in Fig. 3 against the left-hand edge of the array. Of the 31 elements in a column 19 cover the character. Registering pattern.-The lowermost row, Fig. 3, is connected to sampling circuits, one of which responds if the row is all white and another if there are some black signals. To find the character pattern it is necessary to ignore breaks such as that at 15 due to defective printing. For this purpose, three rows are looked at together as the pattern is shifted vertically downwards. The corresponding 3- row strips are designated " black " if any are black and the number of adjacent black strips are counted. The character is judged to be present when at least 9 successive overlapping strips are black. The spurious mark 16 is not taken as the base of the character because it is separated by at least one all-white strip of 3 rows. Once the character pattern has been found its lower boundary is known and it can be shifted to the proper registry position. The vertical position in the scanning area of the first character of a row is measured by a counter which is set to 15 and counts down for every black strip in the bottom 15 strips of the store. This count for perfect registry should be eight. Values greater or lesser than this in the counter cause the decoder 154, Fig. 12, to generate a signal to alter the vertical position of the scanning area 18<SP>1</SP> by applying a bias to the Y shift of the cathode-ray tube 23. In normal operation, the integrator 147 receiving the correction signal and integrator 148 receiving a signal from a tachogenerator on the paper feed mechanism cause the successive scanning frames to track over the row of characters. The combined correction signals are also applied to the paper feed motor 151 in such a sense as to reduce the speed of the paper as the deflection of the scan increases. This prevents the scan area leaving the screen of the cathode-ray tube altogether. In each row scan the scanning area scans first the edge of the paper at 51, Fig. 7, then the nine character positions 53-61 across the paper and finally the other edge area 52. The areas of paper within the two scanning areas 51 and 52 are compared and a difference signal developed for the purpose of correcting the horizontal registration of the scan with respect to the paper. If the bottom 15 rows of the store 90 are all white, a special mode of scanning is initiated to search for the character. This may happen at the beginning of certain rows of characters due to faulty printing. The special scans are quick and overlap each other. Eventually, a recognition signal indicates that the character has been found and the rest of the row is scanned as before in successive areas each displaced with respect to the last to follow the moving characters. If no recognition signal occurs, the operator of the machine either inserts the character or makes a mark at the appropriate position. Elimination of spurious marks.-The marks 16 and 17 by shifting the character downwardly through the storage array and, after the 19 stages containing the character have passed below the 11th row, turning all black signals to white until the bottom edge of the pattern moving down from the top of the store approaches row 11. Recognition.-After the pattern has been properly registered in the store, the elements are connected to a recognition circuit consisting of an array of diodes designed to give an output on one of twelve leads for each of twelve predetermined patterns of signals in the store. To accommodate remaining slight lack of vertical register the pattern is shifted successively into eight different positions for recognition. The character identified may be punched into a record. Specification 850,582 also is referred to.