An apparatus has a photodetector with a plurality of pixels arranged in at least one dimension. The apparatus is designed to optically pick up an image of an information code by the pixels of the photodetector. In the apparatus, an establishing unit establishes a preliminary correcting region on part of the image data. A preliminary correcting unit provides a correcting variable that estimates a shift amount of the image data; and preliminarily corrects the part of the image data within the preliminary correcting region based on a value of the correcting variable. A determining unit determines whether the preliminary correction of the preliminary correcting unit is proper based on the corrected result. When the determining unit determines that the preliminary correction of the preliminary correcting unit is proper, a correcting unit corrects the image data based on the value of the correcting variable.