COLOR IMAGE FORMING APPARATUS

摘要

PROBLEM TO BE SOLVED: To enhance printing quality by changing the transmission frequency of a first oscillator until the output signal of a comparing means enters a predetermined range, and controlling the output signal of a first detection means and the output signal of a second oscillator so as to allow phase difference between them to enter a predetermined range. SOLUTION: In a control circuit 31 receiving the signal input from both detectors reducing the position of a rotary polygon mirror and an image carrier to control the phase difference between them so as to allow the same to enter a specific range, a TOP delay circuit 40 outputs an inputted vertical synchronous signal TOPSNS signal to a reference BD signal generator 41 as a delayed signal SYTOP to output the signal same to the BD signal inputted from a detector at a time of steady rotation and the signal same in cycle but different in phase to a comparator 42. The comparator 42 compares the inputted signals VDE 0-BDE 7 with the BD signal and outputs the output signals to a control circuit 34. A control circuit 43 outputs a signal S1 changing in oscillation signal according to inputted CMP 0-CMP 7 to a variable oscillator.