Image reading apparatus

An image reading apparatus which reads an original image by scanning said original image, main scan line by main scan line, with a fixed time interval, said apparatus comprising:

• first and second patterns which are located outside of an image reading area, a first pattern comprising a plurality of lines each extending at a fixed angle with respect to a sub-scan direction, a second pattern comprising 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 which reads said first and second patterns as well as said original image;
• a position error measuring portion which measures first and second image reading position errors corresponding to different angle oblique lines of image data obtained as a result of reading said first and second patterns, respectively, said position error measuring portion compensating for position deviations of said first and second patterns using said first and second image reading position errors, and obtaining position-deviation-compensated image reading position errors;
• and
• a position error correcting portion which corrects image data obtained as a result of said image reading portion reading said original image, using said position-deviation-compensated image reading position errors.

A computer program product for measuring image reading position errors in image data which is obtained as a result of scanning an original image, main scan line by main scan line, with a fixed time interval, and correcting said image data using said image reading position errors, said measuring of said image reading errors using first and second patterns which are located outside of an image reading area, a first pattern comprising a plurality of lines each extending at a fixed angle with respect to a sub-scan direction, a second pattern comprising a plurality of lines each extending at a fixed angle but having a reverse direction with respect to the sub-scan direction, said computer program product comprising a computer usable medium having computer readable program code means embodied in said medium, said computer program code means comprising:

• program code means for causing a computer to measure first and second image reading position errors corresponding to different angle oblique lines of image data obtained from reading said first and second patterns, respectively;
• program code means for causing said computer to correct position deviations of said first and second patterns using said first and second image reading position errors, and obtaining position-deviation-corrected image reading position errors;
• and
• program code means for causing said computer to correct image data read by said image reading apparatus, using said position-deviation-corrected image reading position errors.

A computer-implemented method for measuring image reading position errors in image data which is obtained as a result of scanning an original image, main scan line by main scan line, with a fixed time interval, and correcting said image data using said image reading position errors, said measuring of said image reading errors using first and second patterns which are located outside of an image reading area, a first pattern comprising a plurality of lines each extending at a fixed angle with respect to a subscan direction, a second pattern comprising a plurality of lines each extending at a fixed angle but having a reverse direction with respect to the subscan direction, said computer-implemented method comprising the steps of;

• a) measuring first and second image reading position errors corresponding to different angle oblique lines of image data obtained from reading said first and second patterns, respectively;
• b) compensating for position deviations of said first and second patterns using said first and second image reading position errors, and obtaining position-deviation-compensated image reading position errors;
• and
• c) correcting image data read by said image reading apparatus, using said position-deviation-compensated image reading position errors.