Automatic exposure control device

Claim 2

In an automatic exposure control apparatus for photographic cameras of the type including an exposure regulating means movable between maximum and minimum light transmission positions to control the amount of scene light reaching a film plane, first and second oppositely poled coils for driving said regulating means in respectively opposite directions, and means for selectively energizing said coils to adjust the position of said regulating means, the improvement comprising separate means for energizing said second coil to drive said regulating means to its minimum light transmitting position.

Claim 3

In an automatic exposure control apparatus, the improvement claimed in claim 1, further characterized by: a. said selective energizing means comprising a multivibrator electrically coupled to said coils and controlled by a photoresponsive element to drive said regulating means in accordance with the amount of light detected by the photoresponsive element; b. first and second switch means, said first switch means being coupled to said multivibrator to control the activation thereof, said second switch means being coupled to said separate energizing means to control the activation thereof; and c. means coupling said switch means together for activating said multivibrator when said separate energizing means is deactivated and for deactivating said multivibrator when said separate energizing means is activated.

Claim 4

In an automatic exposure control apparatus, the improvement claimed in claim 1, wherein said separate energizing means comprises: a. a pair of transistors each having base, emitter, and collector terminals; b. means for connecting said second coil in series between the respective collector-emitter paths of said transistors; and c. means for rendering said transistors conductive.

Claim 5

In an automatic exposure control apparatus, the improvement claimed in claim 3, wherein said means for rendering said transistors conductive comprises: a. a third transistor having base, collector, and emitter electrodes, the emitter-collector path of said third transistor being coupled to the respective bases of said pair of transistors so that said third transistor is adapted to supply bias potential to the base of said pair of transistors; and b. first switch means for selectively applying bias potential to the base of said third transistor.

Claim 6

In an automatic exposure control apparatus, the improvement claimed in claim 4 further comprising means effective upon conduction of said pair of transistors for automatically determining the time during which said transistors remain conductive.

Claim 7

In an automatic exposure control apparatus, the improvement claimed in claim 5 wherein said time determining means comprises a capacitance means and circuit means for charging said capacitance means, said capacitance means being connected with the bases of said pair of transistors.

Claim 8

In an automatic exposure control apparatus, the improvement claimed in claim 4, further comprising means for terminating the conduction of said pair of transistorS at the end of a predetermined interval regardless of the conductive state of said third transistor.

Claim 9

In an automatic exposure control apparatus, the improvement claimed in claim 6, further comprising: a. circuit means for discharging said capacitance; and b. means for closing said discharging circuit means when said selective energizing means is activated.

Claim 10

In an automatic exposure control apparatus, the improvement claimed in claim 8, wherein said closing means comprises: a. a fourth transistor having base, collector, and emitter electrodes, the collector-emitter path of said fourth transistor being connected as a series element in said discharging circuit means; b. second switch means for selectively applying bias potential to the base of said fourth transistor, said first and second switch means being coupled to alternately bias said third and fourth transistors, respectively; and c. means effective upon operation of said switches in one position for closing said last-mentioned bias applying means to turn on said fourth transistor.

Claim 11

In an automatic exposure control apparatus of the type including adjustable exposure aperture means movable between closed and open positions for controlling the amount of light transmitted to a film plane, transducer means having a close coil and an open coil of respectively opposite polarities for moving the exposure aperture means between its closed and open positions, and actuatable means for selectively energizing said coils, the improvement comprising: a. separate means for energizing said close coil to move the exposure aperture means to its closed position when the means for selectively energizing said coils is deactuated; and b. means effective upon activation of said separate energizing means for determining the time interval during which said close coil is energized.

Claim 12

In an automatic exposure control apparatus of the type including adjustable exposure aperture means movable between closed and open positions for controlling the amount of light transmitted to a film plane, transducer means having a close coil and an open coil of respectively opposite polarities for moving the exposure aperture means between its closed and open positions, and actuatable means for selectively energizing said coils, the improvement comprising: a. separate means for energizing said close coil to move the exposure aperture means to its closed position when the means for selectively energizing said coils is deactuated; and b. means effective upon activation of said separate energizing means for determining the time interval during which said close coil is energized.

Claim 13

In an automatic exposure control apparatus, the improvement claimed in claim 10, wherein said time interval determining means comprises a capacitance network.

Claim 14

In an automatic exposure control apparatus, the improvement claimed in claim 11, further comprising means effective before activation of said time interval determining means for discharging said capacitance network.

Claim 15

In an automatic exposure control apparatus for photographic cameras of the type including an exposure regulating member movable between minimum and maximum light transmitting positions for controlling the amount of light transmitted to a film plane, electromechanical transducer means mechanically coupled with the exposure regulating member for moving the member between those positions, photoresponsive circuit means electrically connected to said transducer means for controlling the movement of the exposure regulating member in accordance with light received from a scene, and means for actuating the photoresponsive circuit means, the improvement comprising: means for moving the exposure regulating member to its minimum light transmitting position when the photoresponsive circuit means has been deactuated.

Claim 16

In an automatic exposure control apparatus for photographic cameras of the type including an exposure regulating member movable between minimum and maximum light transmitting positions for controlling the amount of light transmitted to a film plane, electromechanical transducer means mechanically coupled with the exposure regulating member for moving the member between those positions, photoresponsive circuit means electrically connected to said transducer means for controlling the movement of the exposure regulating member in accordance with light received from a scene, and means for actuating the photoresponsive circuit means, the improvement comprising: means for moving the exposure regulating member to its minimum light transmitting position when the photoresponsive circuit means has been deactuated.