Patent ID: 6904245

Claim:
An image forming apparatus comprising: charging means for charging an image bearing member; exposure means for exposing the image bearing member, which has been charged to form an electrostatic latent image; developing means for developing the electrostatic latent image with developer; transferring means, to which a transferring bias under constant voltage control is applied, for transferring a developer image on the image bearing member onto an other member; test pattern forming means for forming a test pattern for image control on the image bearing member by supplying developer by said developing means on an area of the image bearing member in which charging by said charging means is effected and exposure by said exposure means is not effected; test pattern detection means for detecting the test pattern, which has been transferred to the other member by said transferring means; and control means for setting a value of the transferring bias upon transferring of the test pattern onto the other member in accordance with a surface potential of the image bearing member upon formation of the test pattern.