An image forming device that is capable of performing transfer of paper constantly in a highly accurate manner, irrespective of types or conditions of paper. The image forming device is provided with a motion sensor in a paper transfer path thereof for detecting the surface condition of an idle roller moving in accordance with the paper, and transfer of the paper is controlled on the basis of surface condition signals generated by the motion sensor. The motion sensor makes laser light, which is irradiated by a semiconductor laser, hit on an outer peripheral surface of the idle roller that rotates accompanying the transfer of paper and the reflected light is received by a two-dimensional semiconductor image sensor. Then, the surface condition signals are detected on the basis of speckle patterns generated in the reflected light.

 
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