Patent ID: 8023845

Claim:
An image forming apparatus comprising: a rotatable photosensitive member; a charging member configured and positioned to charge said photosensitive member; an applying unit configured to apply, to said charging member, a charging bias voltage comprising an oscillating voltage component of a predetermined frequency and a constant voltage component in each cycle; an exposure unit configured and positioned to form an electrostatic image by exposing said photosensitive member on the basis of image information inputted thereto; and executing means for executing an operation, on the basis of the image information inputted, in a first mode or a second mode selected in accordance with a speed of said photosensitive member and a resolution of an image to be outputted, wherein in the first mode, a duration of the constant voltage component is a first predetermined duration, and in the second mode, the duration of the constant voltage component is a second predetermined duration which is different from the first predetermined duration.