Patent ID: 8238804

Claim:
An image forming apparatus comprising: a forming portion configured to form an image on an object based on image data, said object being capable of movement relative to said forming portion; a control portion configured to provide data of a mark as said image data for said forming portion; a light receiving portion configured to receive light from a detection area, a level of said light varying with time while an image formed on said object moves across said detection area with said relative movement of said object; a determining portion configured to determine a position of said mark in a relative movement direction of said object based on comparison of a time-varying level of said light with at least one threshold during movement of said mark on said object across said detection area; a correcting portion configured to correct said determined position of said mark by a correction value into a corrected mark position, said correction value being set to a higher value if a slope of level change of said light when the level of said light exceeds said threshold or falls below said threshold is smaller while said mark on said object moves across said detection area; and an adjusting portion configured to adjust a position of an image to be formed by said forming portion based on said corrected mark position.