Image forming method

An image forming method, comprising:

• scanning a plurality of photoconductor bodies with a plurality of light beams in a first direction inside a housing to form a plurality of electrostatic latent images on the plurality of photoconductor bodies;
• detecting at least one of the plurality of light beams on a first light receiving face that is perpendicular to the first direction and provided inside the housing;
• detecting at least one of the plurality of light beams on a second light receiving face that is non-parallel to the first light receiving face and provided inside the housing;
• detecting at least one of the plurality of light beams on a third light receiving face that is non-parallel to the first light receiving face and provided outside the housing;
• developing the plurality of electrostatic latent images with developers to form a plurality of images;
• transferring the plurality of images onto an image conveyor;
• forming a pattern for correcting positional displacement of the plurality of images to be transferred onto the image conveyor;
• detecting the pattern for correcting positional displacement of the plurality of images to be transferred onto the image conveyor;
• calculating a first set of amounts of positional displacement of the plurality of images to be transferred onto the image conveyor based on detection of the pattern;
• measuring a first time period between detection of at least one of the plurality of light beams on the first light receiving face and detection of at least one of the plurality of light beams on the second light receiving face;
• calculating a second set of amounts of positional displacement of the plurality of images to be transferred onto the image conveyor based on the first time period;
• measuring a second time period between detection of at least one of the plurality of images on the second light receiving face and detection of at least one of the plurality of light beams on the third light receiving face;
• determining timing of calculation of the first set of amounts of positional displacement of the plurality of images based on the second time period;
• and
• controlling timing of light exposure of the plurality of photoconductor bodies to the plurality of light beams based on the first set of amounts of positional displacement of the plurality of images and the second set of amounts of positional displacement of the plurality of images.