An image forming apparatus includes a rotating body to form an image, a sensor to detect a home position of the rotating body, a processor to acquire image density data of the image formed by the rotating body in odd-numbered rotation and even-numbered rotation of the rotating body separately based on a rotation home position signal output by the sensor, extract an image density fluctuation caused by a rotation of the rotating body, and correct an image forming condition based on the image density fluctuation.

An image forming apparatus includes a rotating body to form an image, a sensor to detect a home position of the rotating body, a processor to acquire image density data of the image formed by the rotating body in odd-numbered rotation and even-numbered rotation of the rotating body separately based on a rotation home position signal output by the sensor, extract an image density fluctuation caused by a rotation of the rotating body, and correct an image forming condition based on the image density fluctuation.

A cylinder scanner includes a base, a contact image sensor module, a first roller unit, a second roller unit and an adjusting mechanism. The contact image sensor module is mounted on a middle of an upper surface of the base for scanning a cylinder. The first roller unit is slidably disposed above the middle of the upper surface of the base. The second roller unit is slidably disposed above the middle of the upper surface of the base. The adjusting mechanism is connected between the first roller unit and the second roller unit. When the cylinder is scanned, the first roller unit and the second roller unit rotate in the same direction, the cylinder is positioned on the first roller unit and the second roller unit, so the cylinder is driven by the first roller unit and the second roller unit to rotate.