Patent ID: 7471307

Claim:
An electrophotographic image forming apparatus comprising: n-number (where n is a natural number and n≧2 holds) of photosensitive bodies for carrying toner images that differ from one another; n-number of light sources for forming latent images on respective ones of said n-number of photosensitive bodies; a rotating polygonal mirror for causing light beams, which are emitted from said n-number of light sources, to be deflected and to scan across corresponding ones of said photosensitive bodies; developing units for forming toner images by developing the latent images formed on said photosensitive bodies owing to scanning by said rotating polygonal mirror; a transfer body to which are transferred the toner images formed on said photosensitive bodies; a sensing device for sensing an amount of color misregistration with regard to each of the toner images that have been formed on said transfer body; a selecting device for selecting a mirror surface of said rotating polygonal mirror, which is used in the scanning of every one of the photosensitive bodies, in such a manner that the amount of color misregistration of every one of the toner images will be less than (n−1)/n pixels; and a control device for controlling light-emission timing of said light sources in such a manner that the light beams from said light sources will be deflected and scanned by the selected minor surfaces, wherein said sensing device is a unit for sensing amounts of color misregistration regarding the toner images of colors other than a prescribed color of a toner image; and said selecting device is a unit for selecting the minor surfaces of said rotating polygonal mirror that correspond to said other colors, with the mirror surface of said rotating polygonal minor that corresponds to the prescribed color being adopted as a reference, and wherein if the amounts of color misregistration of the other colors are represented by A, B and C in order of decreasing value, then said selecting device: selects, with regard to colors corresponding to A and B, the mirror surface that is one surface rearward, in direction of rotation, of the minor surface that corresponds to the prescribed color if B is positive and B−|C| is positive; selects, with regard to a color corresponding to C, the mirror surface that is one surface forward, in direction of rotation, of the minor surface tat corresponds to the prescribed color if B is positive and B−|C| is not positive; selects, with regard to a color corresponding to A, the mirror surface that is one surface rearward, in direction of rotation, of the mirror surface that corresponds to the prescribed color if B is not positive and A−|B| is equal to or greater than zero; and selects, with regard to colors corresponding to B and C, the mirror surface that is one surface forward, in direction of rotation, of the mirror surface that corresponds to the prescribed color if B is not positive and A−|B| is not equal to or greater than zero.