Patent ID: 7515162

Claim:
An image forming apparatus comprising: an input unit that inputs an image forming job; a raster image generating unit that interprets the input image forming job and successively generates a set of raster images of respective colors; a transport path along which continuous paper is transported; a plurality of image forming engines each of which is individually driven in accordance with a driving signal supplied thereto to successively form each color image on a surface of the continuous paper transported along the transport path and form a pattern indicating a position as a reference for image formation so that the pattern is not overlapped with the image; a calculating unit that calculates displacement amount between the formation position of the pattern formed by each image forming engine and an ideal formation position thereof; and a controller that (1) supplies each of the plurality of image forming engines with a driving signal instructing formation of a blank image when the calculated displacement amount is larger than a second threshold value, (2) supplies each of the plurality of image forming engines with a driving signal instructing formation of the image corresponding to each raster image generated by the raster image generating unit and a preset mark when the calculated displacement amount is smaller than the second threshold value, and (3) supplies each of the plurality of image forming engines with a driving signal instructing formation of only the image corresponding to each raster image generated by the raster image generating unit when the calculated displacement amount is smaller than a first threshold value, the first threshold value being smaller than the second threshold value.