Patent ID: 6934504

Claim:
An image forming apparatus comprising: an image forming unit for forming an image on a sheet; registration rollers for conveying the sheet to said image forming unit at a predetermined timing; a sheet reading unit which has a plurality of reading pixels used to read an image on the sheet, and is arranged on a passage region of the sheet between said image forming unit and said registration rollers so that the plurality of reading pixels line up in a widthwise direction of the sheet; a leading end detector for detecting a leading end of the sheet by repetitively reading out the plurality of pixels at a predetermined period; a start timing determination unit for determining a start timing of image formation of said image forming unit on the basis of the leading end of the sheet detected by said leading end detector; a re-convey unit for making said image forming unit form a predetermined image on the sheet in accordance with the start timing of image formation determined by said start timing determination unit, and re-conveying the sheet formed with the predetermined image to said image forming unit; an image position detector for detecting a predetermined image position-formed on the sheet re-conveyed by said re-convey unit by reading out the reading pixels of said sheet reading unit; a correction value calculation unit for calculating a correction value of the start timing of image formation in the convey direction on the basis of the image position detected by said image position detector; and a forming start position adjustment unit for adjusting a position of an image to be formed on the sheet by said image forming unit by correcting the start timing of image formation in the convey direction on the basis of the correction value calculated by said correction value calculation unit.