GB1399348A - Character recognition apparatus - Google Patents

Abstract

1399348 Character recognition systems MEL EQUIPMENT CO Ltd 5 July 1972 [2 Aug 1971 6 Aug 1971] 36251/71 and 37057/71 Heading G4R A character field is regarded as being divided into a matrix of elementary areas, signals representing the character field are applied to a set of " black " logic masks to identify the character. The character field signals are shifted relative to the masks to provide a match signal whenever the character and a mask match. The number of matches from each mask is counted and a mask identifies the character if its count exceeds a certain threshold number. Each mask is associated with a respective " white " mask which inhibits the black masking if it detects a black elementary area (character portion) where a white area (backbround) should be. The number of white areas viewed by a white mask is small relative to the number of background areas in the field of the corresponding character. The embodiment disclosed employs raster scanning or a clocked column of photo-cells to provide serial signals representative of the elementary areas of the field. To compensate for any drop outs in the character, i.e. white areas within the character strokes, the field is effectively scanned by a 2 x 2 matrix of areas. If a particular one of these areas is black the remaining areas are set to black. This is done by feeding the character signals to a shift register, four relevant stages of the register feeding an OR gate, Figs. 11, 12 (not shown). The corrected character is read in to a shift register store, parallel signals from the store feeding the masking circuits. As the character rolls through the store the number of matches occurring during, for example, 6 rolls following detection of the first match is counted, the counter whose count exceeds a preset threshold identifying the character. The white masks inhibit the black masking, as indicated above. A further mask is provided to enable the counters only when a character is horizontally centred in the store. The mask inspects elementary areas corresponding to the two outer columns and some central columns of a matrix field represented by the shift register store, the counter being inhibited if either or both outer columns include a black bit and if any of the central columns is all white, Figs. 13, 14 (not shown). The mask match counters may each have thresholds corresponding to a character having thick, medium, or thin strokes. The character is identified by that counter which exceeds the threshold for the thickest strokes. If two or more counters exceed the thickest threshold the character may be identified by taking account of the relative times of occurrence of the match signals.