GB1487114A - Single read station acquisition and character recognition - Google Patents

Abstract

1487114 Optical scanning system RECOGNITION EQUIPMENT Inc 29 April 1975 [15 Aug 1974] 17772/75 Heading G4R Characters in spaced lines, e.g. an address on an envelope are scanned, a digitized signal is produced and stored and data from a selected line of the characters is read from the store. An image of a moving data carrying document is formed on a photodiode array 30 which may contain a line of 512 photodiodes. Data from the array is fed to an A/D converter 44 which forms a stream of four bit words representing the output values of the photodiodes. These signals feed a correlator 48 which produces a series of binary signals each bit of which corresponds to the output of a respectively photodiode. The bits are fed serially to a memory 52 containing a plurality of shift registers. The document is scanned in strips with data from each strip being fed into the memory. A line top/bottom detector 54 is used to detect the presence of a predetermined line of print, e.g. the lowest line and determines where the top and bottom of this line is. This detector is used to determine skew and to enable read out of the lowest line. The memory 52 may store all the data from the photocells or may act as a buffer holding sufficient scans to allow the lowest line to be detected. For instance higher lines may extend further than the lower lines and so be detected as the lowest line before the true lowest line is scanned (Figs. 5C, 5D, not shown). When the lowest line is read out it may be corrected for skew and normalized for height.