| 摘要 |
PURPOSE:To always assure the optimum exposure state, by varying the shifting speed of an optical system in accordance with the variation of the quantity of light of an exposure lamp if caused by the voltage fluctuation of an AC power supply. CONSTITUTION:In case the voltage of an AC power supply 1 is normal, the AC voltage is supplied to a DC motor 6 which gives the full wave rectification to the AC voltage with a full wave rectifier 5 and moves an optical system. Thus an exposure is carried out. When the voltage of the power supply 1 increases during an exposure to increase the quantity of light of a lamp 2, a Cds18 varies its resistance value R18 according to the change of the quantity of light. As a result the threshold voltage V1 is reduced. With a reduction of the voltage V1, the angle of phase with which a thyristor 17 has ignition varies to apply the voltage to the DC motor 6. Accordingly the number of rotations of the motor 6 increases to accelerate the shifting speed of the optical system. In such constitution, the optimum exposure state is always assured. |
