Patent GB-1097935-A (GB)
Title: Multi-drum document handling character reader
Inventor: CHILDS GEORGE WILLIAM
IPC: G06V10/12
Filed: 1965-10-25
Abstract: 1,097,935. Character recognition: electric signalling. RECOGNITION EQUIPMENT Inc. Oct. 25, 1965, No. 45145/65. Headings G4H and G4R. Document-scanning apparatus comprises a plurality of document-holding drums rotatable about their own axes and symmetrically mounted for stepwise rotation about a main axis parallel to their own axes so that each drum moves successively to load, read and unload stations, each drum when in the read position being rotated and moved axially past an optical scanner. Thus with three drums and stations, three documents are in the system at a time. A document is suction-fed from a first elevator 51 and carried by fibre brushes past a mechanical gate (256) to the drum 60 rotating slowly clockwise at the load station, the edge of the document entering a slot in the drum and the document being held on the drum by suction. At the read station, the drum 61 is rotated quickly clockwise and scanned optically. At the unload station, the drum 62 is rotated at the slow speed anticlockwise and the document stripped off by fingers entering circumferential grooves in the drum surface. The document is then carried by belts 65 to either of two elevators 66, 68, e.g. for successfully and unsuccessfully read documents respectively. Read Station.-One line of the document is scanned per revolution of the drum 61, an optical image of part of the document being passed by a lens 76 and mirror 100 to an array of photodetectors 103, 103a. The drum 61 is moved axially by a screw 72, the lens 76 being moved with it by means of gearing 86, 88, a differential drive 89 and a cam 90 except that at the end of each line (revolution) the lens 76 is stepped down one, two or &c. lines (depending on the line spacing) to reach the next line. The latter feature is controlled by an extending portion (103a) of the photodetector array which senses which of the following line positions actually contain lines of characters and produces an output from a corresponding gate (401, Fig. 10, not shown) for each such line. The gates set corresponding bistables (411) but the outputs of the latter are so connected back via diodes that only that corresponding to the next line of print is left set, to energize a corresponding solenoid (381 . . . 416 . . . 417). This solenoid positions a corresponding one of a number of equal struts (370 . . . 418) carried by a pivoted arm (365) at different distances from its pivot, so that when a cam (361) rotating with the drum 61 pushes the arm (at the end of the current line), that strut alone engages a further arm (372) and pushes it a corresponding distance to actuate the differential drive 89 for the lens 76 correspondingly via a cable (383). Signals from the extended portion 103a of the photodetector array also correct for line skew as a line is scanned by controlling the mirror 100. The signals select resistor tappings (471) to supply an analogue voltage on a line (472) to a differentiator (476) and integrators (477 . . . 482). If the integrator outputs are large enough (indicating skew), they select one of a number of struts (432) in a camdriven linkage generally similar to that described before, to rotate the mirror 100, the direction of rotation being selected by the differentiator output via a diode (486). The screw 72 advancing the drum 61 axially is driven by a motor 82 the speed of which is controlled in accordance with an error signal obtained by comparing a present number with the amount of light from a source (282) passing a wedge (281) fixed relative to the lens 76. The effect of this is to minimize the amount of movement necessary to move from line to line. It is mentioned that the documents may be fed on to the drum deliberately skewed in such a way as to reduce drum and lens movement.