| 摘要 |
PURPOSE:To automatically obtain always optimum exposure by adding the output voltage of a photodetecting circuit to the output voltage of a voltage forming circuit, applying the same to a comparator, comparing the same with preset reference voltage and controlling the quantity of light of an exposure lamp. CONSTITUTION:If there is an error between the output voltage of a waveform shaping circuit 34 and the reference voltage from a reference voltage generating circuit 39, the output voltage of an error amplifier 37 increases or decreases in accordance with the size of said error, in accordance with which, the generating phase of the trigger pulse outputted from a trigger pulse generating circuit 41 changes as well. Hence, the conduction angle of a thyristor 32 changes and this change is fed back to the amplifier 37 by the trigger pulse to a spurious load circuit 33. Therefore, the device operates as a whole in such a way that the output voltage of the circuit 34 is made equal to the reference voltage from the circuit 39, that is, the voltage applied across an exposure lamp 2 is made constant at all times against the voltage fluctuations of a power source 31. |
