| 摘要 |
PROBLEM TO BE SOLVED: To minimize the color shift of an output image along an auxiliary scanning direction, in a color image forming device having a plurality of scanning optical systems. SOLUTION: A plurality of scanning optical systems are synchronously controlled by PLL control circuits 55, 56, and color shift correcting control is performed by a color shift correcting control part 51 so that the distance from the end of a transfer material to the image reading position of the optical scanning system is constant for each rotation. A scanner motor 8 is rotated by a scanner clock signal, an FG signal is obtained as information about the rotation of the motor, and the PLL control circuit 55 performs control to accelerate or decelerate the motor 8 so that the phase difference between the scanner clock signal and the FG signal is held constant. An FG signal of the first optical scanning system is also input to the PLL control circuit 56 of the second scanning optical system to control the scanner motor 9 likewise. The color shift correcting control part 51 measures the phase difference between a TOP signal and a BD signal and controls the rotating speed of the motor 50 that drives the transfer drum, so as to hold the phase difference within a certain range. |
