| 摘要 |
PURPOSE:To eliminate latency time and perform rapid copying by setting the power at which optimum exposure is obtained based on the original density measured by preliminarily lighting an exposure lamp until the original reaches the scanning position. CONSTITUTION:The quantity of light of an exposure lamp 1 which was lighted by a preliminary lighting power setting circuit 27 when a copying switch 21 is turned ON assumes a stable state in the time t2. A first timer 22 sends the signal l to a sample holding circuit 24 in the time t2 after the ON of the seitch 21. The signal level m corresponding to the original density of that time is outputted to a power setting circuit 25 by a density detecting element 20. Based on this, the circuit 25 adjusts the bias current flowing in the light-adjusting photo detector of a lamp power control circuit 26 so as to provide optimum exposure light quantity. On the other hand, a second timer 28 changes over the circuit 27 to the circuit 26 in the time when the leading end of the original reaches the scanning position after the ON of the switch 21 and supplies the power which becomes optimum exposure light quantity from the circuit 26 to the lamp 1 at the time t2. Thereby, copying may be rapidly accomplished. |
