Patent ID: 7750934

Claim:
An image forming apparatus comprising: a photosensitive body including a reference mark for specifying a reference position of the photosensitive body when the photosensitive body rotates; an exposure unit configured to expose a surface of the photosensitive body; a detection unit configured to detect the reference mark; a storage unit configured to store correction value for correcting the exposure amount, the correction value corresponds to respective positions of the surface of the photosensitive body in a rotational direction; a recognition unit configured to recognize a exposure position on the photosensitive body based on a timing in which the detection unit detects the reference mark; a calculation unit configured to calculate the correction value by use of the correction value stored in the storage unit and the exposure position recognized by the recognition unit; and a control unit configured to control exposure amount of the exposure unit based on the correction value calculated by the calculation unit, wherein the control unit controls, in the case where a difference between a first correction value being correction value calculated by the calculation unit immediately before detecting the reference mark by the detection unit and a second correction value being correction value calculated by the calculation unit after detecting the reference mark by the detection unit is an allowable change value or less, the exposure amount of the exposure unit based on the second correction amount, and controls, in the case where the difference is more than the allowable change value, the exposure amount of the exposure unit based on the first correction amount and the allowable change value.