Abstract: An image forming apparatus has a plurality of drive motors for driving a plurality of photosensitive drums independently, a plurality of motor rotation controllers for controlling rotation and driving of the plurality of drive motors independently, a plurality of rotation phase detectors for detecting the rotation phase of each one of the plurality of photosensitive drums, a rotation phase difference calculator for calculating the rotation phase difference of the other photosensitive drums corresponding to the rotation phase of the photosensitive drum for black as the reference, a phase correction setting unit for setting the rotation phase difference in printing operation, and a phase correction controller for correcting rotation phase of the other photosensitive drums on the basis of the calculated rotation phase difference and the set rotation phase difference.

Abstract: An image input device includes an image reader capable of realizing conversion of image resolution. The image input device includes a scanner driving unit provided with a resettable resolution arithmetic unit, a resolution interpolating process change-over unit and a resolution interpolating unit. The presettable resolution arithmetic unit sets at a scanner unit a resolution designated by a user unless the designated resolution exceeds a maximum presettable resolution of the scanner. If the user designated resolution exceeds the maximum presettable resolution, the presettable resolution arithmetic unit sets at the scanner a predetermined resolution which does not exceed the maximum presettable resolution. The resolution interpolating processing unit interpolates the image data outputted from the scanner unit for generating the image data of the resolution designated by the user.