Image forming apparatus and control method thereof

A method of controlling an image forming apparatus including an image carrier, an exposure unit that forms an electrostatic latent image by exposing a surface of the image carrier based on image data, a developing unit that develops the electrostatic latent image formed on the image carrier with a developing material, and an intermediate transfer member onto which a developing material image developed by the developing unit is transferred, the method comprising:

• detecting a speed of surface of the intermediate transfer member at a transfer position where the developing material image is transferred from the image carrier to the intermediate transfer member;
• controlling driving of the intermediate transfer member based on a result of detection in the detecting a speed of surface of the intermediate transfer member at a transfer position, so as to make the speed of surface of the intermediate transfer member at the transfer position close to a predetermined target speed;
• detecting a speed of surface of the image carrier at the transfer position;
• controlling driving of the image carrier based on a result of detection in the detecting a speed of surface of the image carrier at the transfer position, so as to make the speed of surface of the image carrier at the transfer position close to the same speed as the speed of surface of the intermediate transfer member at the transfer position;
• detecting a speed of surface of the image carrier at an exposure position where the image carrier is exposed by the exposure unit;
• and
• controlling a timing of exposure by the exposure unit based on a result of detection in the detecting a speed of surface of the image carrier at an exposure position, so as to make an interval to expose the image carrier by the exposure unit in a sub-scanning direction, close to a constant interval.