| 摘要 |
PURPOSE:To execute ideal shutter control, by connecting one terminal of a logarithmic diode and an integration capacitor to an input terminal of an operational amplifier, and connecting the other terminal to an output terminal and a separate electric power supply. CONSTITUTION:When a switch 9 is on and a switch 9' is off, cathode voltage of a logarithmic diode 10 is equal to emitter voltage of an informating leading-in transistor TR2, and anode voltage is led to a display circuit through a follower circuit of an operational amplifier 17. When a terminal (b) of an integral capacitor 12 is connected to an output terminal of the amplifier through a resistance 15, a voltage difference of both terminals of the capacitor 12 becomes zero, therefore, a current of a photodiode 11 nearly becomes a forward current of a logarithmic compression diode 10, and an output which has logarithmically compressed an optical current is obtained in the output terminal of the amplifier 17. When the switch 9 is turned off and the switch 9' is turned on by synchronizing with running of a front curtain, the voltage across the capacitor 12 is zero, instantaneously noninverted input terminal voltage of the amplifier 17 becomes equal to the output voltage of a regulating power supplying circuit 1, and thereafter, this voltage rises, an output of a comparator 18 is inverted, and exposure ends. |
