COLOR IMAGE FORMING DEVICE AND REGISTER MARK DETECTION DEVICE THEREFOR

摘要

PROBLEM TO BE SOLVED: To minimize register-mark detection error caused by flutter of a carrying belt and to obtain satisfactory contrast even in the detection of register marks of arbitrary colors on the carrying belt. SOLUTION: In the color image forming device in which toner images of specific colors formed by an image forming part are superimposed and transferred to a recording medium S carried by a carrying belt 60 and are fixed thereon, a register mark detection device 51 detects register marks formed corresponding with the toner image of several colors on the belt 60 in order to detect the displacement of the toner images of several colors on the medium S. The device 51 comprises two light sensors 511a and 511a' for detecting the same part N of the register mark K1 and two light sources 512a and 512a' corresponding to the sensors 511a and 511a' and used for emitting light to the mark K1, and arranges the sensors and the respective light sources so that they are axially symmetrical with respect to an axis H in the direction of the normal line of the face of the belt 60 on which the mark K1 is formed.