Patent GB-1109349-A (GB)
Title: Line identification apparatus
IPC: G06V30/10
Filed: 1966-07-25
Abstract: 1,109,349. Line identification. INTERNATIONAL BUSINESS MACHINES CORPORATION. 25 July. 1966 [9 Aug., 1965], No. 3309/66. Heading G4R. Line identification apparatus detects coded line representations fixed with respect to a document which bears lines to be identified. Fig. 4 shows a document which bears lines of characters (not shown) to be scanned and read by a cathode ray tube (and photomultiplier),. Sets of coded indicia in a line identification track are provided to allow lines to be identified for subsequent marking when they contain unreadable characters, and to facilitate indexing of the document after one group of lines has been scanned to bring the next group into position. Each set of coded indicia is a set of horizontal bars 19 present or absent to represent 1 and 0 respectively. Thicker so-called bracket bars 17 separate successive sets of the coded indicia. Other bars are provided as shown. The document is advanced until a photodetector 33 has detected both bars 30 and 29 after which it is stopped. The beam of the cathode ray tube is then at 35. The beam is moved rightwards until it encounters bar 27 when it backs off and moves downwards to read coded indicia 26 (bars present and absent) identifying the document. When a predetermined distance below a bracket bar 28, the beam moves rightwards in a line searching raster to find a line of characters. On detecting a line, the raster is normalized and centred on it (no details) as it moves rightwards. When it reaches the right-hand end of the line it returns leftwards to read the characters (no details). If all the characters are read successfully, the beam moves downwards and rasters along the next line. However, if a character could not be read the beam crosses horizontally into the line identification track then moves upwards. During the upward movement until the first bracket bar is detected, a first counter (354, Fig 2e, not shown) counts clock pulses to give a fine component of the line position, this fine component then being transferred to latches (363- 368, Fig. 2e, not shown). The coded indicia detected until the next bracket bar is reached give a coarse component of the line position and are gated into latches (377-382, Fig. 2e, not shown) under control of the decoded (410) output of the first counter (354) now being fed with clock pulses for this purpose. The fine and coarse components are passed to a central processor store. The beam returns downwards along the same path (despite Fig. 4) and after it passes the lower bracket bar, the first counter (354) counts clock pulses until the count equals the latched fine component (363-368) as determined by AND gates (395-401, Fig. 2e, not shown) whereupon the beam moves rightwards to find another line of characters. For indexing the document, the coarse and fine components of the position of the last line to be scanned are obtained and latched as before, the coarse component being passed to further latches (389-394). The document is moved and bars 16, 17 detected at 39 are counted by a second counter (427, Fig. 2f, not shown) preset with the number of bars between the detector 39 and the required stop position. When the count equals the latched coarse component (389-394) as determined by AND gates (428-433, Fig. 2#, not shown), clock pulses are gated to the first counter (354, Fig. 2e, not shown) the count being compared (395-401) with the latched fine component (363-368) of the last line to be scanned prior to indexing. On equality, the document is stopped. The last line to be scanned prior to indexing is now identified by reading successive sets of the coded indicia during downward movement of the beam, latching them (377-382, Fig. 2e, not shown) and comparing them (402-107, Fig. 2f, not shown) with the coarse component (389-394) of said last line. On equality, beam movement continues with counting of clock pulses in the first counter (354, Fig. 2e, not shown) until the count equals (395-401) the fine component (363-368) of said last line. The beam then moves downwards and to the right to scan the next line of characters. Lines can be marked by printing in the line mark track 36 at another station while a further document is being read. As the document moves through the second station, a detector 67 detects the bars 16, 17 which are counted (475, Fig. 2b, not shown) the count being compared (476-482) with the coarse component of the position of the first line to be marked (from the central processor store). On equality, clock pulses are gated to a further counter (485, Fig. 2b, not shown) until the count equals (486-492) the fine component of the line position (from the central processor store) when the marker is actuated. Further lines are marked similarly. Modifications.-In a second embodiment, the document (Fig. 7, not shown) is similar except that thick and thin (rather than present and absent) bars are used to represent 1 and 0, and a bar (56) to stop the document initially is in the line identification track. An 8-bit shift register (515, Figs. 5c, 5g, not shown) is provided for receiving a 5-bit set of document or line identifying indicia (read during downward movement of the beam) and two 1-bits produced by two bracket bars bracketing the set. An AND gate (548, Fig. 5g, not shown) verifies that a valid code has been shifted in, viz. that the first and seventh stages hold 1 (the bracket bars) and the eighth holds 0, and a trigger (550, Fig. 5g, not shown) verifies that an odd number of bits have been shifted in. A fine component is obtained by counting (595, Fig. 5d, not shown) as before. Comparisons of fine component counts are done by entering the complement of the first into the last-mentioned counter (595) and incrementing to capacity. The line identification track could be on a belt or plate referenced with respect to the document, rather than on the document itself.