Patent GB-1093721-A (GB)
Title: A device for reading digits in a series manner
Inventor: SPANJERSBERG ARIE ADRIAAN
IPC: G06V30/10
Filed: 1965-01-01
Abstract: 1,093,721. Automatic character reading. DE STAAT DER NEDERLANDEN, TEN DEZE VERTEGENWOORDIGD DOOR DE DIRECTEUR - GENERAAL DER POSTERIJEN, TELEGRAFIE EN TELEFONIE. Jan. 1, 1965 [Jan. 2, 1964]. No. 113/65. Heading G4R. In character recognition apparatus the characters are identified from data representing the maximum number of intersections in any vertical scan; the height of the first intersection on a central vertical scan as compared with the corresponding height in other scans; the joining of lines in the right- or left-hand half and the height of the second intersection in the central scan as compared with the height of the bottom end of the first intersection of another scan. The character is moved past a registry detection position in which a slit of light falls on the document and is imaged on the screen of a vicidon tube. A vertical scan detects the left-hand edges of the characters when they enter the slit and a flash is fired to image the whole character on the screen. The vertical scan then moves to the extreme right of the character frame and scans back towards the character until the right-hand edge is encountered. The width of the character, thereby obtained, is halved and the scan moved to the central position to make a central scan and a raster moving to the left. Having returned to the initial position a second raster is made from the centre towards the right. In any scan the number of black areas cut is counted by counter Te, Fig. 9, and the output on the three leads a, b, c applied through dividers De to triggers Tr1, Tr2, Tr3. The dividers pass a signal only if the same count is obtained in two adjacent scans. The height of the first black cut in the central scan is measured by charging capacitor C1 until the first black signal appears on lead a. In the same way the first black in any other scan is used to end the charging on capacitor C2. At the end of each scan the gate P14 opens by a signal on terminal e and the charges are compared. If the first black signal appears in any scan at a higher level than that in the central scan the trigger Tr12 is set. Line joins in the right- or left-hand half are found by the circuits involving gates P1, P2 and P6, P7. Gate P6 receives the b output from the counter, indicating a count of two black areas cut by the scan, and the video signal from the scanner Ca. As long as the beam is still on the second black area gate P6 produces a signal which is delayed one scan by delay line Va2. If the first black in the next scan (indicated by the output of gate P7 controlled by the a signal and the video signal) is present at the same time as the delayed signal from gate P6, gate P8 gives a signal. This is used to set one of four triggers Tr6-Tr9 according as to whether the join condition detected is in the right or left half and in the upper and lower half. Signals indicating upper and lower halves are obtained from the position of the second black area in the central scan. Gates P1, P2, P3 detect joins between the second and third black areas and this indication is passed to triggers Tr4 or Tr5 according to whether the signal occurs in the right- or lefthand side of the character. Gate P15 detects shapes such as occur in the character " 4 " where the first black area in the scan which passes down the vertical stem reaches a lower level than the second black area in the centre scan. For this purpose a circuit A is provided to produce a signal 0 which, in each scan, lasts until the level corresponding to the bottom of the second black area in the central scan. The first black area signal a and the video signal are combined in gate P15 with signal 0 and when all are present trigger Tr13 is set. The outputs of the eleven feature triggers Tr1-Tr9, Tr12 and Tr13 are combined to identify the character scanned. A circuit is described for producing the necessary horizontal deflection signals for the scanning sequence.