Patent ID: 8903287

Claim:
An image forming apparatus comprising: a rotating photosensitive member; a light irradiation unit configured to form an electrostatic latent image on the photosensitive member by irradiating the photosensitive member, which is charged, with light; a detection unit configured to detect change of a surface potential of the photosensitive member; and a shielding unit configured to shield part of the light from the light irradiation unit, wherein the light irradiation unit forms an electrostatic latent image pattern on the photosensitive member by irradiating the photosensitive member and the shielding unit with light, wherein the detection unit detects, in a rotation direction of the photosensitive member, timing at which the surface potential changes depending on displacement of the electrostatic latent image pattern in an axial direction of the photosensitive member, and wherein the light irradiation from the light irradiation unit is controlled according to the detected timing.