Circuit arrangement for editing a scanned pattern

Abstract

For compensating tolerances within a photodiode matrix of a scanning unit, in a single scanning process, various momentary, column, displaced positions of a scanning pattern are compared with one another as current image signals. To this end, the plurality of black elements in an image signal to be first intermediately stored in a first image memory is counted in an image element counting device. When the current image signal reproduces a 'fat' character, the white elements of the current image signal and of a correlated image pattern intermediately stored in a second image memory are disjunctively linked with one another in a switching device. Given 'weak' characters, the black elements are employed. Insofar as the direction of the relative velocity between the scanning unit and a recording medium is not prescribed, a plurality of positions of the correlated image signal are to be employed for a comparison in a comparator circuit. This comparison yields the position with the best coincidence. Therefore, a center/left or, respectively, a center/right displacement of the current image signal with respect to the correlated image signal can be compensated by means of a corresponding control of the switching device. The independence of the scanning direction offers an advantage in a preferred use of the circuit arrangement in hand-held reading devices.