Patent ID: 8471881

Claim:
An image forming apparatus, comprising: an image conveyor; plural photoconductor bodies; a light exposure device configured to expose the plural photoconductor bodies to plural light beams to form plural electrostatic latent images on the plural photoconductor bodies; a development device configured to develop the plural electrostatic latent images with developers to form plural images; a transfer device configured to transfer the plural images onto the image conveyor; and a pattern detection device configured to detect a pattern for correcting positional displacement of the plural images to be transferred onto the image conveyor; wherein the light exposure device includes: an optical scanning part configured to scan the plural photoconductor bodies with the plural light beams in a first direction; a first light detection part having a first light receiving face configured to detect at least one of the plural light beams and be perpendicular to the first direction; a second light detection part having a second light receiving face configured to detect at least one of the plural light beams and be non-parallel to the first light receiving face; a third light detection part having a third light receiving face configured to detect at least one of the plural light beams and be non-parallel to the first light receiving face; the optical scanning part, the first light detection part, and the second light detection part being provided inside a housing of the light exposure device; the third light detection part being provided outside the housing; and a light exposure timing control device configured to calculate a first set of amounts of positional displacement of the plural images to be transferred onto the image conveyor based on detection of the pattern, measure a first time period between detection of at least one of the plural light beams on the first light receiving face and detection of at least one of the plural light beams on the second light receiving face, calculate a second set of amounts of positional displacement of the plural images to be transferred onto the image conveyor based on the first time period, measure a second time period between detection of at least one of the plural light beams on the second light receiving face and detection of at least one of the plural light beams on the third light receiving face, determine timing of calculation of the first sets of amounts of positional displacement of the plural images based on the second time period, and control timing of light exposure of the plural photoconductor bodied to the plural light beams based on the first set of amounts of positional displacement of the plural images and the second sets of amounts of positional displacement of the plural images.