Image forming device with forgery prevention

摘要

An image forming device, such as a color copying machine or a color printer, which processes an input image signal, thereby obtains an output image signal, and forms an output image on the basis of the output image signal. In the image forming device, an information input unit writes some information identifying the copying machine to an area in an information storing unit at the time when a power source is turned on for the copying machine for the first time after the assembly thereof. When the power source is turned on for a second and any subsequent times for the copying machine, the copying machine copies an original sheet in such a state of the machine that the information stored in the area of the information storing unit is added to the output image in the form of a pursuit image which it is hard or impossible to recognize with the human eyes.