Verfahren zum Abgleich eines Abtastgerätes

摘要

A process is disclosed for calibrating the optoelectronic scanning member of a scanner which scans an image point by point and line by line and converts the modulated scanning light into image values in a light/voltage converter. Converter densities are first determined and stored as a converter density table depending on different degrees of amplification of the light/voltage converter. The densities of the scanning diaphragms and grey filters used are also determined and stored as diaphragm density and grey filter density tables. A scanner-specific calibration is carried out with a reference diaphragm by adjusting the degree of amplification so that the image value corresponds to a predetermined white level. When a document-specific calibration is later carried out, the required amplification is automatically determined from the stored density tables and the white point density of the document in question, and the light/voltage converter is adjusted accordingly. This calibrating process considerably shortens the time of preparation required for scanning a document and discharges the operator from routine calibration tasks.