| 摘要 |
PURPOSE:To obtain the copy of always stable background density by providing a reference circuit and comparator. CONSTITUTION:A comparator 16 connected with a bias correcting circuit 18 and reference circuit 19 is connected between a detector 10 which detects the toner image of a reference target and various control circuits 22. As a result of this, the background density detection signal of the detector 10 is inputted to the comparator 16 through the amplifying circuit 12 connected with a drift compensating circuit 13 and gain adjusting circuit 14 and sample holding circuit 15, where it is compared with the preset reference value from the reference circuit 19, by the results whereof, at least one of the exposure lamp control circuit 22b and charge current control circuit 22d is controlled by the specified control mode by way of a central control circuit 20 and output circuit 21, thus the copy having always the stable background density is obtained irrespective of ambient environments and aging. |
