Shutter control circuit for controlling exposure time under low light conditions

Claim 2

In a camera having actuatable shutter means for regulating the amount of scene light projected toward a film exposure plane therein, a light sensitive control circuit for producing a shutter control signal having a time dependent parameter related to light intensity which determines the open time of said shutter means, and means responsive to said control signal for actuating said shutter means to terminate the film exposure interval when said time dependent parameter equals a predetermined value, improved exposure control apparatus for regulating said actuatable shutter means under low ambient light conditions comprising: a. circuit means, including photosensitive means, adapted to switch between (1) a first state when ambient light intensity exceeds a predetermined level and (2) a second state when ambient light intensity is less than said predetermined level; b. signal means connected to said circuit means for producing an indicator signal when said circuit means is in said second state, which indicator signal indicates ambient light is inadequate to effect a particular film exposure value within a predetermined exposure time; and c. means responsive to the presence of said indicator signal for modifying said shutter control signal to increase said time dependent parameter thereof to indicate a light intensity greater than the intensity of ambient light whereby the shutter open time is reduced for time intervals greater than said predetermined exposure time.

Claim 3

In a camera having an actuatable shutter mechanism and a control circuit including a photosensitive element adapted to produce a control signal having a light dependent parameter which determines the open time of said shutter mechanism, the improvement comprising: a. switch means coupled to said photosensitive element having a first deenergized state when ambient scene light is greater than a predetermined level and a second energized state when ambient light is less than said predetermined level; b. energizable means connected to said switch means for producing an auxiliary signal when said switch means is energized, which auxiliary signal indicates ambient light is insufficient to produce a particular film exposure value within a predetermined time; and c. means responsive to the existence of said auxiliary signal for altering said control signal to effectively indicate a scene light intensity higher than ambient light whereby the open time of said shutter mechanism is reduced for exposure intervals greater than said predetermined time.

Claim 4

In a camera having an actuatable shutter mechanism and a control circuit including a photosensitive element adapted to produce a control signal having a light dependent parameter which determines the open time of said shutter mechanism, the improvement comprising: a. switch means coupled to said photosensitive element having a first deenergized state when ambient scene light is greater than a predetermined level and a second energized state when ambient light is less than said predetermined level; b. energizable means connected to said switch means for producing an auxiliary signal when said switch means is energized, which auxiliary signal indicates ambient light is insufficient to produce a particular film exposure value within a predetermined time; and c. means responsive to the existence of said auxiliary signal for altering said control signal to effectively indicate a scene light intensity higher than ambient light whereby the open time of said shutter mechanism is reduced for exposure intervals greater than said predetermined time.

Claim 5

In a camera having actuatable shutter means for regulating the amount of scene light projected toward a film exposure plane therein, improved exposure control apparatus for controlling said shutter means comprising: a. means for producing a primary shutter control signal having a light dependent time constant which determineS the open time of said shutter means; b. light-responsive circuit means having (1) a first, deenergized state when ambient light exceeds a predetermined level and (2) a second, energized state when ambient light is less than said predetermined level; c. signal means connected to said circuit means for producing an indicator signal when said circuit means is energized, which indicator signal indicates ambient light is inadequate to effect a particular film exposure value within a predetermined exposure time interval; d. means responsive to the presence of said indicator signal for producing a secondary shutter control signal; and e. means for combining said primary and said secondary control signals to produce a resultant shutter control signal having a time constant of a shorter duration than said primary signal time constant whereby the open time of said shutter means is reduced for exposure times greater than said predetermined exposure time interval.

Claim 6

In a camera having actuatable shutter means for regulating the amount of scene light projected toward a film exposure plane therein, improved exposure control apparatus for controlling said shutter means comprising: a. means for producing a primary shutter control signal having a light dependent time constant which determineS the open time of said shutter means; b. light-responsive circuit means having (1) a first, deenergized state when ambient light exceeds a predetermined level and (2) a second, energized state when ambient light is less than said predetermined level; c. signal means connected to said circuit means for producing an indicator signal when said circuit means is energized, which indicator signal indicates ambient light is inadequate to effect a particular film exposure value within a predetermined exposure time interval; d. means responsive to the presence of said indicator signal for producing a secondary shutter control signal; and e. means for combining said primary and said secondary control signals to produce a resultant shutter control signal having a time constant of a shorter duration than said primary signal time constant whereby the open time of said shutter means is reduced for exposure times greater than said predetermined exposure time interval.

Claim 7

In a camera having actuatable shutter means for regulating the amount of scene light projected toward the camera film exposure plane, improved exposure control apparatus for controlling said actuatable shutter means under low ambient light conditions comprising: a. circuit means for controlling said actuatable shutter means to terminate the exposure interval, said circuit means including photosensitive means for producing a primary shutter control signal having a particular light dependent parameter to effect a predetermined shutter open interval in accordance with the intensity of scene light; b. means responsive to ambient light for producing an auxiliary signal when the intensity of ambient light is inadequate to effect a particular exposure value within said predetermined shutter open interval; and c. means for adding said auxiliary signal to said primary shutter control signal to produce a resultant shutter control signal to regulate said actuatable shutter means such that the interval in which said shutter means is opened is reduced for shutter open intervals greater than said predetermined shutter open interval.

Claim 8

In a camera having actuatable shutter means for regulating the amount of scene light projected toward the camera film exposure plane, improved exposure control apparatus for controlling said actuatable shutter means under low ambient light conditions comprising: a. circuit means for controlling said actuatable shutter means to terminate the exposure interval, said circuit means including photosensitive means for producing a primary shutter control signal having a particular light dependent parameter to effect a predetermined shutter open interval in accordance with the intensity of scene light; b. means responsive to ambient light for producing an auxiliary signal when the intensity of ambient light is inadequate to effect a particular exposure value within said predetermined shutter open interval; and c. means for adding said auxiliary signal to said primary shutter control signal to produce a resultant shutter control signal to regulate said actuatable shutter means such that the interval in which said shutter means is opened is reduced for shutter open intervals greater than said predetermined shutter open interval.

Claim 9

In a camera having actuatable shutter means for automatically regulating the amount of scene light projected toward a film exposure plane therein, improved exposure control apparatus for regulating said actuatable shutter means under low ambient light conditions comprising: a. circuit means, including photosensitive means, adapted to switch between (1) a first state when ambient light intensity exceeds a predetermined level and (2) a second state when ambient light intensity is less than said predetermined level; b. means defining a source of illumination having a first non-conductive state when said circuit means is in said first state, said first state being indicative that ambient light is sufficient to effect a particular film exposure value within a predetermined period of time, and a second conductive state when said circuit means is in said second state for emitting an optical signal, said optical signal being indicative that ambient light is insufficient to effect such an exposure value within said predetermined period of time; c. a control circuit, including said photosensitive means, having a particular parameter related to the amount of projected scene light and adapted to produce a shutter control signal having a time constant which determines an open time for said shutter means; d. means for directing said optical signal onto said photosensitive means to modify said particular parameter to lower the time constant of said shutter control signal to effectively indicate a higher level of ambient light; and e. means responsive to said shutter control signal for actuating said shutter means to terminate the film exposure interval when said signal reaches a predetermined amplitude.

Claim 10

In a camera having actuatable shutter means for automatically regulating the amount of scene light projected toward a film exposure plane therein, improved exposure control apparatus for regulating said actuatable shutter means under low ambient light conditions comprising: a. circuit means, including photosensitive means, adapted to switch between (1) a first state when ambient light intensity exceeds a predetermined level and (2) a second state when ambient light intensity is less than said predetermined level; b. means defining a source of illumination having a first non-conductive state when said circuit means is in said first state, said first state being indicative that ambient light is sufficient to effect a particular film exposure value within a predetermined period of time, and a second conductive state when said circuit means is in said second state for emitting an optical signal, said optical signal being indicative that ambient light is insufficient to effect such an exposure value within said predetermined period of time; c. a control circuit, including said photosensitive means, having a particular parameter related to the amount of projected scene light and adapted to produce a shutter control signal having a time constant which determines an open time for said shutter means; d. means for directing said optical signal onto said photosensitive means to modify said particular parameter to lower the time constant of said shutter control signal to effectively indicate a higher level of ambient light; and e. means responsive to said shutter control signal for actuating said shutter means to terminate the film exposure interval when said signal reaches a predetermined amplitude.

Claim 11

Exposure control apparatus as set forth in claim 5 wherein said optical signal directing means comprises a light pipe.

Claim 12

In a camera having actUatable shutter means for regulating the amount of scene light projected toward a film exposure plane therein and a control circuit for producing a shutter control signal having a time dependent parameter related to scene light intensity which determines the open time of said shutter means, improved exposure control apparatus for regulating said actuatable shutter means comprising: a. circuit means, including photosensitive means, adapted to switch between (1) a first state when ambient light intensity exceeds a predetermined level and (2) a second state when ambient light intensity is less than said predetermined level; b. means energizable when said circuit means is in said second state for producing an electrical control signal, said control signal being indicative that ambient light is inadequate to effect a particular film exposure value within a predetermined time period; c. means for adding said electrical control signal to said shutter control signal to produce a resultant shutter control signal having a resultant time dependent parameter which effectively indicates a scene light intensity that is greater than the intensity of the ambient light; and d. means for actuating said shutter means to terminate the film exposure interval when said resultant time dependent parameter equals a predetermined value.

Claim 13

In a camera having actUatable shutter means for regulating the amount of scene light projected toward a film exposure plane therein and a control circuit for producing a shutter control signal having a time dependent parameter related to scene light intensity which determines the open time of said shutter means, improved exposure control apparatus for regulating said actuatable shutter means comprising: a. circuit means, including photosensitive means, adapted to switch between (1) a first state when ambient light intensity exceeds a predetermined level and (2) a second state when ambient light intensity is less than said predetermined level; b. means energizable when said circuit means is in said second state for producing an electrical control signal, said control signal being indicative that ambient light is inadequate to effect a particular film exposure value within a predetermined time period; c. means for adding said electrical control signal to said shutter control signal to produce a resultant shutter control signal having a resultant time dependent parameter which effectively indicates a scene light intensity that is greater than the intensity of the ambient light; and d. means for actuating said shutter means to terminate the film exposure interval when said resultant time dependent parameter equals a predetermined value.

Claim 14

In a camera having actuatable shutter means for regulating the amount of scene light projected toward a film exposure plane therein and a control circuit including a light sensitive element having a particular parameter related to the intensity of ambient light and being adapted to produce a control signal having a time constant functionally related to said particular parameter, which time constant determines the open time of said shutter mechanism, the improvement comprising: a. voltage-sensitive switching means coupled to said light-sensitive element and having an output which is deenergized when ambient light is greater than a predetermined level and which is energized when ambient light is less than said predetermined level; b. means for defining a source of illumination energizable to produce an optical signal when said voltage-sensitive switching means output is energized, said optical signal being indicative that ambient light is insufficient to effect a particular film exposure value within a predetermined shutter open time; c. means for directing said optical signal onto said light-sensitive element to modify said particular parameter thereof to effectively indicate a scene light intensity which is higher than the intensity of the ambient light; and d. means for actuating said shutter means to terminate the film exposure interval when the amplitude of said shutter control signal is equal to a predetermined level whereby the shutter open time is reduced for exposure intervals greater than said predetermined shutter open time.

Claim 15

In a camera having actuatable shutter means for regulating the amount of scene light projected toward a film exposure plane therein and a control circuit including a light sensitive element having a particular parameter related to the intensity of ambient light and being adapted to produce a control signal having a time constant functionally related to said particular parameter, which time constant determines the open time of said shutter mechanism, the improvement comprising: a. voltage-sensitive switching means coupled to said light-sensitive element and having an output which is deenergized when ambient light is greater than a predetermined level and which is energized when ambient light is less than said predetermined level; b. means for defining a source of illumination energizable to produce an optical signal when said voltage-sensitive switching means output is energized, said optical signal being indicative that ambient light is insufficient to effect a particular film exposure value within a predetermined shutter open time; c. means for directing said optical signal onto said light-sensitive element to modify said particular parameter thereof to effectively indicate a scene light intensity which is higher than the intensity of the ambient light; and d. means for actuating said shutter means to terminate the film exposure interval when the amplitude of said shutter control signal is equal to a predetermined level whereby the shutter open time is reduced for exposure intervals greater than said predetermined shutter open time.