| 摘要 |
PURPOSE:To simplify constitution of a voltage controller by applying a signal with a required magnitude to a deviation signal of a negative feedback type electrometer detecting electrostatic latent image potential in a white ground part of a manuscript and by using an output of the electrometer as development bias voltage. CONSTITUTION:Deviation electrostatic latent image potential taking, as reference, potential by an electric field fluctuation device C corresponding to a manuscript white ground part of a photosensitive drum 1 is detected with an electric field voltage converter A of a probe P of a negative feedback type potentiometer further in response to this deviation electric potential, high voltage of a high voltage power source HT is applied to voltage detected by a synchronous detector C of a main body part MB by a high voltage controlling circuit E, allowing the potentiometer NFEM to be controlled with negative feedback. Accordingly when an output of the potentiometer NFEM is applied as developing bath voltage to a development electrode 2a of a developing device 2, development bias voltage control stable over a long period is performed with simple constitution that uses the electrometer and a high voltage source for a development bias together. Further also when a signal with required polarity or a phase is applied to the deviation signal, the same can be done. |
