Patent ID: 7922278

Claim:
An image printing apparatus comprising: a printing section that performs printing on a print target medium; a moving section that can move in a predetermined main scan direction; an edge-detecting section that is mounted on the moving section and outputs, by utilizing photoelectric conversion, a voltage that changes across each edge of the print target medium; a position-detecting section that detects a position of the moving section; a reference stage that has one edge and another edge in such a manner that the reference stage has a predetermined reference width therebetween, the reference stage being formed in such a manner that the edge-detecting section outputs a voltage that changes across each edge of the reference stage; and a calibrating section that commands the moving section to move in such a manner that the edge-detecting section passes through the one edge and the another edge of the reference stage, commands the position-detecting section to detect the position of the moving section at a point at which a voltage outputted by the edge-detecting section changes during movement of the moving section at each measured position, calculates a measured width based on each measured position, and calibrates the edge-detecting section based on the measured width and the reference width; wherein the calibrating section commands the position-detecting section to detect, as a first measured position, the position of the moving section at a point at which a voltage outputted by the edge-detecting section changes during the movement of the moving section in which, as the moving section moves, the edge-detecting section moves from a surface area of the reference stage so as to pass through the one edge of the reference stage, and thereafter, the calibrating section commands the position-detecting section to detect, as a second measured position, the position of the moving section at a point at which a voltage outputted by the edge-detecting section changes during the movement of the moving section in which, as the moving section moves, the edge-detecting section moves from the surface area of the reference stage so as to pass through the another edge of the reference stage; the calibrating section calculates a calibration value in proportion to a difference between the measured width and the reference width; and the calibrating section performs calibration by subtracting the calibration value from a position of one edge of the print target medium detected by the edge-detecting section and by adding the calibration value to a position of another edge of the print target medium detected by the edge-detecting section.