Exposure control device for camera
AssigneeCanon Kabushiki Kaisha
InventorsMasaharu Kawamura, Yoshihiro Shigeta, Masanori Uchidoi, Yoji Sugiura, Hiroshi Yamamoto
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Abstract
An exposure control device for a camera having a first counter which performs analog-to-digital conversion for a photometric purpose and a second counter for sequence control of each part of the camera. For use of a self-timer, the first and second counters are connected in series with each other to use them in a state of having their steps added together. Upon completion of a self-timer photographing operation, the first and second counters are separated from each other and are brought back into their original conditions.
Claims4
An exposure control device for a camera comprising:
- photographing information signal producing means, said means producing an analog signal in accordance with photographing information;
- constant voltage producing means for producing a constant voltage;
- standard voltage producing means for producing a standard voltage;
- an operational amplifier to whose inverting input terminal the analog signal and the constant voltage are applied and to whose non-inverting input terminal the standard voltage is applied;
- a condenser connected between the inverting input terminal and the output terminal of the operational amplifier, said condenser being charged when the analog signal is applied to the operational amplifier and discharged when constant voltage is applied;
- a comparator to whose first input terminal the output of the operational amplifier is applied and to whose second input terminal the standard voltage is applied, said comparator being inverted when the output of the operational amplifier reaches the standard voltage;
- first switching means, provided between the photographing information signal producing means and the inverting terminal of the operational amplifier, for forming a charging path for the condenser when said first switching means is actuated;
- second switching means, provided between the constant voltage producing means and the inverting input terminal of the operational amplifier, for forming a charging path for the condenser when said second switching means is actuated;
- pulse producing means for producing pulses;
- a counter for counting the number of pulses from the pulse producing means and for stopping the counting, when the inverted signal from the comparator is applied, so as to produce a signal for controlling the exposure;
- said counter producing alternatively a signal for actuating the first switching means and a signal for actuating the second switching means;
- reset-enable-signal producing means for producing a signal enabling the resetting of the counter for a certain determined time from the release operation start;
- and
- gate means for resetting the counter, being applied with the inverted signal from the comparator when the reset-enable-signal is being applied, the condenser being discharged down to the standard voltage when the counter has been reset by means of said gate means.
Dependencies are inferred from the claim text.