Patent ID: 7147316

Claim:
An image forming device for transferring a medium to be printed on in order to perform image formation, the image forming device comprising: transfer means for transferring the medium to be printed on; drive means for driving the transfer means; an observation object having a surface to be moved directly or indirectly by the transfer means; surface condition signal generating means for irradiating the observation object with light having coherency, receiving the reflected light reflected by the surface of the observation object and generating signals with respect to the surface condition of the observation object in accordance with the received reflected light; moving amount detecting means for calculating a moving amount of the observation object by chronologically comparing the surface condition signals generated by the surface condition signal generating means; and control means for controlling the drive means based on detection results of the moving amount of the observation object, which moves when the transfer means is driven by the drive means, obtained by the moving amount detecting means.