| 摘要 |
<p>An improved automatic exposure time control device for cameras is composed of mechanical and electronical parts. A means is provided for converting the brightness of the object to be photographed into the control current including a photosensitive element and a capacitor wherein a differential amplifier is integrated, one input of said amplifier is subjected to a voltage proportional to logarithm of the brightness of the object and the other is subjected to a voltage in response to the exposure factors. Further an indicator is connected between said input terminals and another manually adjustable resistor is provided for manual control. The control current which sets exposure time is compensated for automatically by the circuit including the differential amplifier and the indicator with regard to the characteristics of the photosensitive element. When the mechanism is switched to manual control the measuring circuit having the indicator also acts as the interlocked exposure meter, and the exposure time may selectively coincide with either the indicated optimum value or the arbitrary deviated under-or over-exposure value.</p> |
