Patent ID: 7495683

Claim:
An image forming apparatus comprising: an image forming portion for forming an image on an image carrier, for primarily transferring the image on the image carrier onto an intermediate transfer member having a plurality of marks indicative of reference positions, to thereby form a color image, and for secondarily transferring the image on the intermediate transfer member onto a recording material to thereby carry out image formation; a detecting portion for detecting the marks on the intermediate transfer member; a controller for causing an image write reference signal, which is to be used to start image formation, to be generated based on an output from said detecting portion; and a determining portion for determining whether or not detection of the marks by said detecting portion is normal, wherein said controller causes the image write reference signal to be generated based on detection of ones of the marks which are determined to be normal by said determining portion, and causes an alternate signal, serving as the image write reference signal, to be generated in association with any of the marks which are determined to be abnormal.