Patent ID: 7830402

Claim:
An image forming apparatus capable of successively forming images on a first surface and a second surface of a transfer material and fixing the images, comprising: a plurality of image carriers; a plurality of light scanning devices that respectively form latent images on said plurality of image carriers by scanning light beams based on image data in accordance with an image clock; a plurality of beam detectors that respectively detect the light beams from the plurality of light scanning devices and output horizontal synchronization signals; a changing device that changes, when image formation is carried out on the second surface, a frequency of the image clock based on an expansion/contraction ratio of the transfer material after fixing of the images on the first surface; and an adjusting device that adjusts write start positions of the plurality of light scanning devices, wherein said adjusting device adjusts, when image formation is carried out on the first surface, the write start positions of the plurality of light scanning devices based on respective first values corresponding to numbers of image clock pulses from detection of the respective horizontal synchronization signals to write start timings such that a misregistration between the latent images formed by the plurality of light scanning devices is reduced, and wherein said adjusting device adjusts, when image formation is carried out on the second surface, the write start positions of the plurality of light scanning devices based on respective second values that are derived from the first values and the expansion/contraction ratio.