Image forming apparatus incorporating position detector and position corrector

An image forming apparatus comprising:

• an image forming device configured to perform an image formation on an image formation surface of a sheet, the image forming device including a transfer device to configured to transfer an image to the image formation surface of the sheet;
• a pair of detectors including an upstream side detector and a downstream side detector disposed downstream from the upstream side detector in a sheet conveying direction, the upstream side detector and the downstream side detector each configured to detect a position of a first image previously formed on a first surface of the sheet through the image formation of the image forming device while a second surface of the sheet is the image formation surface, the upstream side detector and the downstream side detector each being contact image sensors (CISs) oriented to face the first surface of the sheet with the first image previously formed thereon while the second surface of the sheet is the image formation surface;
• a holding body configured to, while holding the sheet such that the second surface of the sheet is the image formation surface with the first surface of the sheet having the first image previously formed thereon, perform one of a rotation in a radial direction about a support shaft attached thereto in a direction perpendicular to an axial direction thereof and a lateral shift in a width direction of the sheet, in response to an instruction;
• and
• a controller configured to,
• analyze the position of the first image on the first surface of the sheet obtained by the pair of detectors by determining a difference in the position of the first image as detected by the upstream side detector and the position of the first image as detected by the downstream side detector to generate an analysis result, and
• generate the instruction to cause the holding body to perform the one of the rotation and the lateral shift to match a relative position of the first image previously formed on the first surface of the sheet with a second image to be formed on the second surface of the sheet based on the analysis result such that a position that the second image is subsequently formed on the second surface after the one of the rotation and the lateral shift is based the upstream side detector and the downstream side detector each detecting the position of the first image previously formed on the first surface while the second surface of the sheet is the image formation surface.