Optical document reading circuit and associated filter - includes bar of photocells scanning line by line with filtering circuit comparing successive output signals to minimise errors

摘要

The document device includes a lighted window (6) illuminating one line of a document (7). An optical system forms an image of the illuminated line on a bar (1) of photosensitive cells. A parallel - series storage register (2) is connected to the outputs from the bars of photocells (1) to provide signals (e j) relating to each of the cells in the bar. A filter (3) receives the signal (ej) and provides output signals (sj) which are transmitted to utilisation circuit. The circuits (1,2) are charge coupled devices (CCD) the former comprising a bar of 1728 photocells. The register includes two parallel-series registers whose outputs are switched alternately. The filtering circuit compares signals from successive cells in order to provide error-free output signals.