Image forming apparatus and method of correcting color registration

A method of forming a color image, comprising:

• scanning a first group of light beams associated with a first group of monochromic images on a first group of photosensitive members by deflecting the first group of light beams with a beam deflector toward the first group of photosensitive members, the beam deflector including a double mirror portion having a first group of one or more mirrors coplanar with respect to each other and a second group of one or more mirrors that are not coplanar with the first group of one or more mirrors, the double mirror portion being configured to pivot about a pivotal axis that extends substantially parallel to the surfaces of the first and second groups of one or more mirrors such that respective light beams deflected by the first group of one or more mirrors and the second group of one or more mirrors are out of phase with respect to each other by a deflected phase difference, the first group of light beams being deflected off the first group of one or more mirrors of the beam deflector to form a first group of latent images on the first group of photosensitive members;
• scanning a second group of light beams associated with a second group of monochromic images on a second group of photosensitive members by deflecting the second group of light beams off the second group of one or more mirrors of the beam deflector toward the second group of photosensitive members to form a second group of latent images on the second group of photosensitive members, the second group of latent images being substantially in phase with the first group of latent images;
• developing the first group of latent images by applying thereto a first group of monochromic colored toner to form a first group of monochromatic toner images on the first group of photosensitive members;
• developing the second group of latent images by applying thereto a second group of monochromic colored toner to form a second group of monochromatic toner images on the second group of photosensitive members;
• and
• transferring the first group of monochromic toner images and the second group of monochromic toner images onto a transfer medium in phase to overlap one another to form the color image on the transfer medium,
• wherein a distance between a first photosensitive member from the first group of photosensitive members and a second photosensitive member from the second group of photosensitive members, along a sub-scanning direction of the image forming apparatus, corresponds to an odd multiple of half of a distance the transfer medium travels during a pivot period of the beam deflector during which the double mirror portion completes a pivot within a range of its pivoting motion.

A color image forming apparatus, comprising:

• a plurality of photosensitive members;
• a beam deflector configured to scan light beams on the plurality of photosensitive members to thereby form thereon electrostatic latent images, the beam deflector including a double mirror portion having a first mirror and a second mirror, respective surfaces of which are not coplanar, the double mirror portion being configured to pivot about a pivotal axis that extends substantially parallel to the surfaces of the first and second mirrors such that respective light beams deflected by the first mirror and the second mirror are out of phase with respect to each other by a deflected phase difference;
• and
• a transfer member configured to receive from the plurality of photosensitive members a plurality of monochromatic images to overlap one another to thereby form a color image,
• wherein a first two adjacent ones of the plurality of photosensitive members being spaced apart from each other along a sub-scanning direction of the color image forming apparatus by a first distance, a second two adjacent ones of the plurality of photosensitive members being spaced apart from each other along the sub-scanning direction by a second distance different from the first distance.