Patent ID: 8644734

Claim:
An image forming apparatus, comprising: a plurality of photosensitive media; a driving unit configured to rotate the plurality of photosensitive media; a detecting unit configured to detect a rotational state of each of the plurality of photosensitive media; and a controller configured to control the driving unit based on the rotational state of each of the plurality of photosensitive media detected by the detecting unit, the controller being configured to control the driving member in such a manner that two adjacent ones of the plurality of photosensitive media stop with a phase angle difference therebetween, the phase angle difference satisfying a formula: θ = q ⁢ ⁢ 360 ⁢ ( L - π ⁢ ⁢ D ) π ⁢ ⁢ D wherein θ is the phase angle difference between the two adjacent photosensitive media, L being the distance between the two adjacent ones of the plurality of photosensitive media, D being the diameter of at least one of the plurality of photosensitive media, and q being an integer that represents an ordered position respectively of the remaining ones of the plurality of photosensitive media in an order from closest to furthest from the first one of the plurality of photosensitive media, wherein the detecting unit comprises a reference member disposed on each of the plurality of photosensitive media, the reference member having an arc shape and having a length that is sufficient for detection of the rotational angle of the photosensitive media of 170 degrees, and wherein the reference member disposed on each of the plurality of photosensitive media corresponding to a start point of a same imperfection on each of the plurality of photosensitive media.