| 摘要 |
PURPOSE:To control the quantity of light of an exposure lamp continuously by varying the frequency and duty ratio of an oscillation circuit based on a dimming control input, obtaining a dimming signal through the integration of an integration circuit, and controlling the phase of an exposure lamp based on the dimming signal. CONSTITUTION:When an original has high density and the quantity of transmission is small, a CPU 24 controls the oscillation frequency of an oscillation circuit 1 to a lower frequency and a rectangular wave signal of low frequency is supplied to the integration circuit 3. The integration circuit 3 has its resistance value selected so that a charging time is extremely short and a discharging time if long, and the integration output raises gradually to a specific level and is supplied to the deviation value detecting circuit 5 of an automatic voltage controller 4. A phase control circuit 6 controls the phase of the exposure lamp 13 based on its level. When an original has low density and the quantity of light transmitted through the original is large, the frequency of the oscillation circuit 1 is high and the integration output rises gradually to a level higher than the level when the frequency is low, so that this level is supplied to the automatic voltage controller 4. |
