Exposure time control circuitry for cameras
First Claim
1. An exposure time control circuit for a camera adapted for manual and automatic exposure control, comprising:
- a photoelectric element responsive to scene brightness;
a fixed resistor;
means for controlling the exposure;
a variable resistance element including a first and a second independently movable member for varying the resistance between the end terminals of said variable resistance element, said first movable member being at least movable in accordance with the setting of the film sensitivity and said second movable member being movable in accordance with the manually set exposure time;
first switching means having a first position for connecting said first movable member to one of said end terminals and a second position to connect said second movable member to said one end terminal;
manually operable second switching means having a first position for connecting a first output signal formed between said photoelectric element and said variable resistance element to said means for controlling the exposure with said first switching means in said first position, and a second position for connecting a second output signal formed between said fixed resistor and said variable resistance element to said means for controlling the exposure with said first switching means in said second position;
a capacitor for selectively storing said first or second output; and
third switching means having an open position for selectively isolating said capacitor from said first and second outputs and a closed position for connecting said capacitor to said first or second outputs in accordance with the position of said second switching means, said means for controlling being responsive to the signal stored by said capacitor.
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Abstract
In an exposure time control circuit for a camera adapted for manual and automatic exposure control, the resistance of a single variable resistance element is varied by a first movable member moved in accordance with at least the setting of the film sensitivity and by a second movable member moved in accordance with the manually set exposure time. Switching means connect either the first or the second independently movable member into the time control circuit. A manually operable second switching means set to a first position produces a first output signal between a photoelectric element and the variable resistance and in a second position produces a second output signal formed between a fixed resistor and the variable resistance element.
The first independently movable member may also be moved in accordance with the diaphragm aperture setting. The means for switching the first and second independently movable members may be interlocked with the second switching means controlling the automatic or manual mode of exposure control. An indication of the optimum exposure control may be provided in either the automatic or manual exposure control mode in a further modification of the apparatus which includes an additional switch associated with the variable resistance element and which is independently operable from the second means for switching.
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Citations
20 Claims
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1. An exposure time control circuit for a camera adapted for manual and automatic exposure control, comprising:
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a photoelectric element responsive to scene brightness; a fixed resistor; means for controlling the exposure; a variable resistance element including a first and a second independently movable member for varying the resistance between the end terminals of said variable resistance element, said first movable member being at least movable in accordance with the setting of the film sensitivity and said second movable member being movable in accordance with the manually set exposure time; first switching means having a first position for connecting said first movable member to one of said end terminals and a second position to connect said second movable member to said one end terminal; manually operable second switching means having a first position for connecting a first output signal formed between said photoelectric element and said variable resistance element to said means for controlling the exposure with said first switching means in said first position, and a second position for connecting a second output signal formed between said fixed resistor and said variable resistance element to said means for controlling the exposure with said first switching means in said second position; a capacitor for selectively storing said first or second output; and third switching means having an open position for selectively isolating said capacitor from said first and second outputs and a closed position for connecting said capacitor to said first or second outputs in accordance with the position of said second switching means, said means for controlling being responsive to the signal stored by said capacitor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. An exposure time controlling circuit for a camera comprising:
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a photoelectric element responsive to scene brightness; a constant resistor; manually operable first switching means for alternatively selecting one of said photoelectric element or said constant resistor to be electrically connected in the circuit; a pair of terminals; a variable resistance element having first and second movable members for varying the resistance between said pair of terminals, said first movable member being movable in accordance with at least one manual exposure information setting other than manual exposure time setting and said second movable member being movable in accordance with manual exposure time setting; second switching means for connecting one of said first or said second movable members to vary the resistance between said pair of terminals; means for controlling the exposure time responsive to a first output determined by said first switching means selecting said photoelectric element and the resistance between said pair of terminals as determined by said second switching means connecting said first movable member, or a second output determined by said first switching means selecting said constant resistor and the resistance between said pair of terminals as determined by said second switching means connecting said second movable member; a capacitor for storing said first or second output; and third switching means for selectively isolating said capacitor from said first and second output, said controlling means being responsive to the stored output of said capacitor. - View Dependent Claims (17, 18, 19, 20)
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Specification