Patent ID: 8886068

Claim:
An image forming apparatus including: a light emitter configured to emit a light beam; a polygon mirror configured to scan a surface of a photosensitive member that is charged with the light beam emitted from the light emitter by a charging unit to form an electrostatic latent image on the photosensitive member; a detector configured to detect the light beam to be used in scanning by the polygon mirror; a developer unit configured to visualize a toner image by causing a toner to adhere to an electrostatic latent image formed on a surface of the photosensitive member; a transferring unit configured to transfer the toner image to a transferred medium at a transfer nip portion; a transferring voltage applying unit configured to apply a transferring voltage to the transferring unit; and a transferring controller configured to detect a current flowing through the transferring unit according to the application of the transferring voltage to determine the transferring voltage to be applied to the transferring unit based on the detection result; the image forming apparatus further comprising: a measuring unit configured to cause the light emitter to forcibly emit continuously through an image region of the photosensitive member and a non-image region when the polygon mirror is activated to measure a speed of the polygon mirror based on a detection cycle of the detector; wherein the transferring controller determines a reference transferring voltage by correcting the transferring voltage at which detected current becomes a target current in a state that the light emitter is forcibly emitted when the polygon mirror is activated, such that a difference of each of the detected currents when an exposed portion and an unexposed portion of the photosensitive member reach the transfer nip portion is eliminated.