Patent GB-1419105-A (GB)
Title: Process and apparatus for elementary analysis of a printed surface
IPC: G06V10/20
Filed: 1972-12-01
Abstract: 1419105 Pattern recognition systems COMPAGNIE HONEYWELL BULL 1 Dec 1972 [2 Dec 1971] 55599/72 Heading G4R The system involves the processing of the scanned field to produce a modified pattern for recognition. The field is considered as a matrix of elementary areas. Each point of the modified pattern has a state dependent upon the states of a number of areas of the field. A number of areas (e.g. 4) symmetrically disposed about a first area in the field are examined to generate X and Y components of a notional contrast vector V which depends upon the image density in the respective areas. The X and Y components are used to select the nearest vector of a set of, for example, 8 reference vectors V0, V1, &c., these vectors being spaced at 45 degrees increments. The selected reference vector is represented by 4 unity component vectors and 4 zero component vectors v1-v8. These component vectors are spaced at 45 degrees increments and are displaced 22¢ degrees from the reference vectors. The unity component vectors are symmetrically disposed about the reference vector, e.g. as shown by v1-v4 in Fig. 4a for reference vector V2. Component vectors are derived similarly for all the areas in the field. A point in the modfied pattern is developed from the resulting array of component vectors by considering the ratio of the number of unity component vectors and the number of zero component vectors in two symmetrical concentric arrays about the point. In Fig. 5, for example, the boxes 1-12 represent the contrast vectors V in a portion of the field, each vector position corresponding to a first elementary area as described above. The 8 component vectors v1-v8 associated with vector 8 are indicated, unity component vectors being shown as black dots and zero component vectors as white dots. In this example, for a point P in the modified pattern, a symmetrical array of 12 vectors V is considered. Of the associated array of component vectors two from each of the vectors 1-4 (e.g. those shown connected by lines to vector 3) and one from the vectors 5-12 are selected. The ratio of the number of unity component vectors to the number of zero component vectors is determined. Dependent on the ratio a black or a white image element is generated for this point P in the modified image. Other elements of the image are derived similarly. In an apparatus for performing the above steps, for each area of the scanned field the coded values of the density (blackness) of 4 surrounding points are fed to subtractors to provide signals representing the resultant density along the X and Y axes. These represent the components of the contrast vector V. Provided that a function of these signals is sufficiently large a logic unit develops a signal from X and Y. indicating the corresponding nearest reference vector, and from this signal gates develop a 4-bit signal indicative of the unity component vectors v. These signals are stored, together with an indication of their spatial position. The values of the component vectors in an array about each point P are summed to determine whether that point P in the modified image shall be considered as black or white, as described above in respect of Fig. 5.