Method for sensing paper skew and method for correcting paper skew

A method for correcting a paper skew adapted for a device having a paper feeding mechanism, wherein the device has a feed sensor which is fixed at a start position of paper feeding;

• and, a position sensor which moves in a direction perpendicular to a direction of paper feeding and passes through a first position and a second position, wherein the first position is the intersection of a moving path of the position sensor and a line, wherein the feed sensor is on the line, and the line is parallel to the direction of paper feeding, the method for correcting the paper skew comprising:
• the device having a first distance which is a moving distance of a measure paper fed, starting when the measure paper is sensed by the feed sensor and ending when the measure paper is sensed by the position sensor at the first position;
• moving the position sensor to the second position;
• feeding a work paper into the device;
• obtaining a second distance which is a moving distance of the work paper fed, starting when the work paper is sensed by the feed sensor and ending when the work paper is sensed by the position sensor at the second position;
• and
• keeping on feeding the work paper to be processed by the device if the difference between the first distance and the second distance doesn't exceed a threshold value, and modulating contents to be printed on or scanned from the work paper for compensating the paper skew and then keeping on feeding the work paper to be processed by the device if the difference between the first distance and the second distance exceeds the threshold value.