Hitachi, Ltd.

Takashiroh Iwasaki

Kenji Kanemaru

Jun-ichi Mameda

In automatic control systems for cameras, it is highly desirable to be able to conduct automatic continuous photographing under optimum photographing conditions even when a measured light value varies during the photographing operation. To achieve this, a calculation circuit is provided for calculating an amount of electricity to comprise electric information corresponding to the photographing conditions with reference to the measured light value and the sensitivity of the film. Photographing is accomplished in accordance with these photographing conditions by virtue of said automatic control circuit generating a control signal for controlling a shutter mechanism of the camera to end the exposure of the film. The automatic control system includes a memory circuit for memorizing the electric information corresponding to the photographing conditions. A system resetting signal is generated in accordance with a change in the waveform of said control signal after the control signal ends the exposure of the film so that the electric information memorized by said memory circuit is erased.

Automatic control circuit system for cameras provided with a focal-plane

A photometric amplifier circuit, having a photocurrent converting element connected between a pair of inverting and noninverting input terminals of a differential amplifier, for amplifying an electric signal responsive to the quantity of light, is characterized in that a differentiating circuit is connected between the inverting input terminal of the differential amplifier and a power supply to thereby prevent the differential amplifier from producing an undesired latch output when the power is supplied from the power supply, with the result that, after this power is supplied, a normal amplifying operation is capable of being obtained at an earlier time. This invention is particularly adapted for an automatic exposure control system for cameras to precisely control the exposure of the camera.

Amplifier circuit having photoelectric converter

An automatic control circuit system for cameras provided with a focal-plane shutter having front and rear screens, in which a battery voltage is supplied into the automatic control circuit system via a semiconductor switching element when a first release switch of a two-step release switch of a two-step release switch is closed. When a second release switch is closed, the rear screen starts running. A potential for electrically turning on the semiconductor switching element when the first release switch is closed is applied to a control electrode of the switching element. The automatic control circuit system is provided with an electric signal holding circuit, which is triggered with an electric signal generated when the second release switch is closed, to hold at the output terminal of the control electrode an output signal whereby an electric signal for electrically turning on the semiconductor switching element is held in the control electrode and retain the supply of the battery voltage into the automatic control circuit system. The electric signal holding circuit is triggered in response to a rear screen control signal whereby the starting of running of the rear screen of the focal-plane shutter is instructed, to reverse the holding of the output signal so that the semiconductor switching element is electrically turned off with the supply of the battery voltage into the automatic control circuit system stopped.

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Tokyo, Japan

Takashiroh Iwasaki