| 摘要 |
PURPOSE:To always obtain a stable image with high quality, by controlling both the electric charge amount and the exposure volume from the result obtained by comparing the surface potential of a photosensitive drum corresponding to the black and white parts of a reference pattern with the reference value. CONSTITUTION:A reference pattern 3 is formed with a black part 3a and a white pattern 3b, and the surface potential of a photosensitive drum corresponding to the pattern 3 is detected by a surface electrometer 17. In such constitution, the output of the electrometer 17 is supplied to a CPU19 via an A/D converter 18. The CPU19 compares the potentials of the black and white parts with the reference value respectively. Based on the result of this comparison, both the output of an electric charge power supply and the output which increases and decreases the lamp light volume by the unit value are stored. And an electric charge power supply 22 and a lamp power supply 24 are controlled in the next copy cycle and from the contents of the above-mentioned storage. As a result, the aging of a drum and the initial change after a pause of copy can be compensated to ensure a high-quality image at all times. |
