| 摘要 |
PURPOSE:To increase the number of sheets capable of printing by measuring the bright part potential and dark part potential of a photoreceptor, taking the difference of both thereof, correcting the quantity of AC electric charge and controlling the bias voltage during developing. CONSTITUTION:First, the bright part potential and dark part potential of a photoreceptor in standard conditions as references are measured with a surface elctrometer, and reference electrostatic contrast Vc<o> is calculated by a control circuit and is beforehand selected. Next, with an actual electrostatic latent image, its dark part potential and bright part potential are measured, and electrostatic contrast Vc is calculted by the control circuit. This is compared with the reference value Vc<o>, and such AC electric charging conditions under which the electrostatic contrast is made constant are calculated. Next, AC charging is applied on the photoreceptor, after which the dark part potential and bright part potential are measured and the bias voltage to be applied to a developing device is so controlled that the contrast Vc attains a constant value, whereby the electrostatic contrast is compensated. Such compensation is accomplished at every one time of copying. |
