| 摘要 |
PURPOSE:To correct the influence that the ripple of the light quantity of a copy lamp exerts on an image density and to form a high-quality image by forming a voltage change reference signal such as zero cross pulse in accordance with the supply power source to the copy lamp and changing the developing bias of a developing device in accordance with this voltage change reference signal. CONSTITUTION:A CPU 3 receives the zero cross pulse and, therefore, at which timing the ripple is generated is recognized by the copy lamp 4. Then, a PWM signal PWM 2 is outputted in such a manner that the developing bias value varies according to this timing. The ripple of the development bias is thus purposely created in the direction of negating the light quantity ripple. The light quantity of the copy lamp generates the light quantity ripple as the voltage meeting the duty ratio is applied by the PWM signal PWM 1 outputted in accordance with the zero cross pulse. On the other hand, the PWM signal PWM 2 is outputted in accordance with the PWM signal PWM to the developing device and the developing bias is applied in accordance therewith, by which the developing bias ripple is generated. |
