Image reading apparatus

摘要

First and second patterns are located outside of an image reading area. A first pattern comprises a plurality of lines each extending at a fixed angle with respect to a sub-scan direction. A second pattern comprises a plurality of lines each extending at a fixed angle but having a reverse direction with respect to the sub-scan direction. An image reading portion reads the first and second patterns. A position error measuring portion measures first and second image reading position errors corresponding to different angle oblique lines of the first and second patterns of image data obtained as a result of reading the first and second patterns, respectively. The position error measuring portion compensates for position deviations of the first and second patterns using the first and second image reading position errors, and obtains position-deviation-compensated image reading position errors. A position error correcting portion corrects image data read by the reading means using the position-deviation-compensated image reading position errors.