| 摘要 |
PURPOSE:To control automatically subject density by detecting the intensity of reflected light from an original, sampling and holding periodically the detection signal of a detector, and adjusting a development bias voltage or the quantity of exposure according to the output of a sample holding circuit. CONSTITUTION:When continuous copying operation is performed, an automatic density controller sends a sampling signal S1 to the 1st sample holding circuit 23 in preliminary exposing operation and a voltage V1 applied from a reflected light detector 21 is inputted and hled. Then, a sampling signal S2 is sent to the 2nd sample holding circuit 24 in return operation and the output voltage V2 of the 1st sample holding circuit 23 is inputted and held. The development bias voltage is adjusted on the basis of the voltage V2 at the start of exposing operation for copying and copy density is controlled automatically according to original density. The detection signal is sampled to correct the output even during the continuous copying operation, so a D/A detector is unnecessary and the copy density is controlled with high precision. |
