| 摘要 |
PURPOSE:To stabilize an image density without receiving the influence of fluctuating factors, by controlling the electric current of an electryfier according to the setting of the potential in a dark part, regulating the quantity of light of an exposing device according to the setting of the potential in a bright part, and controlling the replenishing of a toner with the inclination of a development curve. CONSTITUTION:When the measured potential in a dark part is lower than an ideal value, the signal instructing the increase in an output current is supplied as a control signal 9 to a control circuit 7 for electrostatic charging current. When said potential is high, a decrease in the output current is instructed. The potential in the bright part is detected with a probe 4 for measuring surface potential and is calculated with a surface electrometer 8. The calculated potential is compared with a reference potential by the 2nd comparator contained therein and quantity of light of an illumination lamp 3A is changed by a control circuit 16 for exposure to control the potential in the bright part so that said potential is made equal to the reference value. The potential V(CUT) at the point where the extension of a development curve 21 intersects with the X-axis is determined, where the final potential in the bright part is designated as V(BKG) and the inclination of the curve 21 as gamma. A control circuit 19 for development outputs a control signal 25 for development bias from the value V(BIAS) of the equation I according to said values. The fluctuation in the image density owing to a change in the developability of the developer is thus prevented. |
