Procedure for obtaining white reference data used to correct non-uniformity in a photoelectric cell series.

摘要

In an image scan reader, a white reference plate (3) is attached to a transparent plate on which an original is to be placed. Respective optical densities on a plurality of scanning lines (LA1-LAn, LB1-LBm) are detected, and are averaged within respective regions (RA, RB). The maximum values of the respective averaged densities are selected for each pixel to be used for correcting non-uniformity of CCD cells which is employed in reading the white reference plate and the image of the original.