| 摘要 |
PURPOSE:To obtain stable electrostatic charging potential by limiting a high voltage electric power source for electrostatic charging in such a way that the potential charged to a photoreceptor is made the same as that of the reference potential pattern formed on the non-image parts of the photoreceptor. CONSTITUTION:The potential of the reference pattern 10 formed on the non- image parts of a photoreceptor 1 is first measured with a surface electrometer probe 5 and a surface electrometer 6, and the voltage thereof is held with a sampling and holding circuit 6a. Thereafter, the photoreceptor 1 is charged with an electrostatic charger 8, and the surface potential of the charged photoreceptor 1 is measured with the probe 5 and the electrometer 6. This is compared with the above-described voltage in a differential amplifier circuit 6b. As a result, the output voltage X of the circuit 6b assumes + potential when the charged potential is high and - potential when low. If an arithmetic circuit 6c and a high voltage electric power source 7 for electrostatic charging are controlled in such a way that said output voltage X is made zero volts, the potential charged to the image part of the photoreceptor 1 is kept always equal to the reference potential pattern 10 formed in the non-image parts, and the stable image is obtained. |
