Apparatus for sorting sheets according to their patterns

Claim 1

Apparatus for scanning a sheet comprising: means for illuminating the sheets; scanning means for collecting light from illuminated pixels of a pattern on the sheet; means for moving the sheet relative to the scanning means; an analogue-to-digital converter responsive to signals from the scanning means representative of the intensity of light from each pixel, to produce intensity signals in digital form; means and storing a plurality of sets of signals, each stored set of signals being representative of a different standard pattern; digital correlator means for correlating the digital signals corresponding to the pattern on the sheet, pixel by pixel, with each of the stored sets of standard-pattern signals, the correlating means generating, for each correlation of the patttern on the sheet with a standard pattern, a correlation output signal, where: ##EQU2## and in which: m is the total number of pixels of the patterns; i takes all values between 1 and m, Y i is the i th pixel of the standard, previously-stored pattern, and x i is the i th pixel of the pattern on the sheet, and; sorting means, responsive to the correlation output signals, for diverting the sheet to a destination corresponding to a standard pattern only if the corresponding correlation output signal is higher than the correlation output signals for all other standard patterns.