Electric shutter control circuit for single lens reflex cameras

Claim 2

An electric shutter control circuit for a single lens reflex camera comprising: a. first and second circuit sections, each comprising: a transistor having an emitter-collector electrode circuit Having first and second sides and a base electrode circuit, a constant-voltage source having first and second sides, the first side being coupled to a first side of the emittercollector electrode circuit of said transistor, wherein said constant voltage source comprises the serial connection of a variable resistor and means providing a logarithmic function output, and an operational amplifier responsive to said logarithmic function output for providing between said first and second sides said constant-voltage independent of current therethrough; b. current controlling photosensitive means coupled to a first side of the emitter-collector electrode circuit of the transistor in the first circuit section for controlling the amount of current through such transistor corresponding to the intensity of received light; c. a bias circuit responsive to the current from said photosensitive means for applying a corresponding bias current to the base electrodes of both said transistors in both said circuit sections; d. a capacitor having first and second sides, the first side being coupled to the second side of the emitter-collector electrode circuit of the transistor in the second circuit section, enabling such transistor to provide a constant-current charge to the capacitor; and e. means for providing a source of potential across the second sides of said photosensitive means and said constant-voltage source of said first circuit section and a source of potential across said second sides of said capacitor and constant-voltage source of said second circuit section; f. the variable resistor in at least one of the circuit sections being arranged to provide an adjustable signal corresponding to photographic determining factors.

Claim 3

An electric shutter control circuit according to claim 1 wherein the bias circuit comprises a circuit having an input and output, the input being coupled to the second side of the emitter-collector electrode circuit of the first circuit section and the output being coupled to the base electrode of the transistor in said first circuit section, the circuit of said bias circuit being characterized by a high input impedance at said input so as to have negligible effect on current at the second side of the emitter-collector electrode circuit and comprising a storage means for retaining the signal on the base electrode of the transistor in the first circuit section and thereby maintain a constant collector-emitter current in the first circuit section.

Claim 4

An electric shutter control circuit according to claim 2 wherein the output of said circuit of said bias circuit is also coupled to the base electrode of the transistor in said second circuit section.

Claim 5

An electric shutter control according to claim 3 wherein said circuit of said bias circuit comprises means for disconnecting the storage means from the collector-emitter electrode circuit of the transistor in the first circuit section.

Claim 6

An electric shutter control circuit according to claim 4 wherein the storage means comprises a capacitor and comprising switch means having a first state for preventing charging current from passing through said capacitor and a second state for allowing charging current to pass therethrough.

Claim 7

An electric shutter control circuit according to claim 1 wherein said constant-voltage source comprises a resistor and a diode serially connected together and an amplifier having an input and an output, said input being coupled to said diode, the output of the amplifier comprising one of said first and second sides of said constant-voltage source and the side of the diode which is opposite from said resistor comprising the other side of said constant-voltage source, the amplifier having a feedback circuit from output to input enabling said amplifier to produce across the first and second sides of said constant-voltage source a constant-voltage output corresponding to the signal across said diode.

Claim 8

An electric shutter control circuit for a Single lens reflex camera comprising: a. first and second mutually independent circuit sections, each comprising: a transistor; a constant-voltage source having first and second sides, the first side being coupled to the emitter electrode of said transistor, said constant-voltage source comprising a series circuit comprising a resistor and a diode serially connected together and an amplifier having an input coupled to said diode, the output of said amplifier comprising the constant-voltage circuit first side and the side of the diode opposite from the resistor comprising the constant-voltage circuit second side, said amplifier having a feedback circuit from output to input thereof enabling said amplifier to produce a constant-voltage output between first and second sides of said constant-voltage source corresponding to the signal across said diode; b. current controlling photosensitive means having first and second sides, the first side being coupled to the collector electrode of said transistor of the first circuit section for controlling the amount of current therethrough corresponding to the intensity of received light; c. a bias circuit responsive to the current from said photosensitive means for applying a corresponding bias current to the base electrodes of both transistors in both said circuit sections, causing a voltage from base to emitter electrodes of the transistor in said first section which corresponds to intensity of the received light; d. a capacitor having first and second sides, the first side being coupled to the collector electrode of the transistor in the second circuit section enabling such transistor to provide a constant-current charge to the capacitor; e. a source of potential; and f. means for connecting one of two sides of the source of potential to the second sides of said photosensitive means and said capacitor and to the side of said resistor opposite from said diode and for coupling the other side of said source of potential to the first sides of said constant-voltage sources and to the other side of said diode from said resistor; g. the resistor of at least one of the circuit sections being adjustable so as to provide an adjustable signal corresponding to photographic determining factors.

Claim 9

An electric shutter control circuit for a Single lens reflex camera comprising: a. first and second mutually independent circuit sections, each comprising: a transistor; a constant-voltage source having first and second sides, the first side being coupled to the emitter electrode of said transistor, said constant-voltage source comprising a series circuit comprising a resistor and a diode serially connected together and an amplifier having an input coupled to said diode, the output of said amplifier comprising the constant-voltage circuit first side and the side of the diode opposite from the resistor comprising the constant-voltage circuit second side, said amplifier having a feedback circuit from output to input thereof enabling said amplifier to produce a constant-voltage output between first and second sides of said constant-voltage source corresponding to the signal across said diode; b. current controlling photosensitive means having first and second sides, the first side being coupled to the collector electrode of said transistor of the first circuit section for controlling the amount of current therethrough corresponding to the intensity of received light; c. a bias circuit responsive to the current from said photosensitive means for applying a corresponding bias current to the base electrodes of both transistors in both said circuit sections, causing a voltage from base to emitter electrodes of the transistor in said first section which corresponds to intensity of the received light; d. a capacitor having first and second sides, the first side being coupled to the collector electrode of the transistor in the second circuit section enabling such transistor to provide a constant-current charge to the capacitor; e. a source of potential; and f. means for connecting one of two sides of the source of potential to the second sides of said photosensitive means and said capacitor and to the side of said resistor opposite from said diode and for coupling the other side of said source of potential to the first sides of said constant-voltage sources and to the other side of said diode from said resistor; g. the resistor of at least one of the circuit sections being adjustable so as to provide an adjustable signal corresponding to photographic determining factors.

Claim 10

In a single lens reflex camera an electric shutter control circuit having a trailing camera screen comprising: a. first and second circuit sections, each comprising: a transistor having an emitter-collector electrode circuit having first and second sides and a base electrode circuit, and a constant-voltage source having first and second sides, the first side being coupled to a first side of the emitter-collector electrode circuit of said transistor, wherein said constant-voltage source comprises the serial connection of a variable resistor and means providing a logarithmic function output, and an operational amplifier responsive to said logarithmic function output for providing between said first and second sides said constant-voltage independent of current therethrough; b. current controlling photosensitive means coupled to a first side of the emitter-collector electrode circuit of the transistor in the first circuit section for controlling the amount of current through such transistor corresponding to the intensity of received light; c. a bias circuit responsive to the current from said photosensitive means for applying a corresponding bias current to the base electrodes of both said transistors in both said circuit sections; d. a capacitor having first and second sides, the first side being coupled to the second side of the emitter-collector electrode circuit of the transistor in the second circuit section, enabling such transistor to provide a constant-current charge to the capacitor; e. means for providing a source of potential across the second sides of said photosensitive means and said constant-voltage source of said first circuit section and a source of potential acRoss said second sides of said capacitor and constant-voltage source of said second circuit section; f. switch means having a first state for preventing charging current from passing through said capacitor and a second state for allowing charging current to pass therethrough; and g. means responsive to the signal at the emitter-collector circuit of the transistor in said second circuit section for effecting a control of the trailing camera screen in the camera.

Claim 11

In a single lens reflex camera an electric shutter control circuit having a trailing camera screen comprising: a. first and second circuit sections, each comprising: a transistor having an emitter-collector electrode circuit having first and second sides and a base electrode circuit, and a constant-voltage source having first and second sides, the first side being coupled to a first side of the emitter-collector electrode circuit of said transistor, wherein said constant-voltage source comprises the serial connection of a variable resistor and means providing a logarithmic function output, and an operational amplifier responsive to said logarithmic function output for providing between said first and second sides said constant-voltage independent of current therethrough; b. current controlling photosensitive means coupled to a first side of the emitter-collector electrode circuit of the transistor in the first circuit section for controlling the amount of current through such transistor corresponding to the intensity of received light; c. a bias circuit responsive to the current from said photosensitive means for applying a corresponding bias current to the base electrodes of both said transistors in both said circuit sections; d. a capacitor having first and second sides, the first side being coupled to the second side of the emitter-collector electrode circuit of the transistor in the second circuit section, enabling such transistor to provide a constant-current charge to the capacitor; e. means for providing a source of potential across the second sides of said photosensitive means and said constant-voltage source of said first circuit section and a source of potential acRoss said second sides of said capacitor and constant-voltage source of said second circuit section; f. switch means having a first state for preventing charging current from passing through said capacitor and a second state for allowing charging current to pass therethrough; and g. means responsive to the signal at the emitter-collector circuit of the transistor in said second circuit section for effecting a control of the trailing camera screen in the camera.

Claim 12

An electric shutter control circuit for a single lens reflex camera comprising: a. first and second mutually independent circuit sections, each comprising a transistor, and a constant-voltage source having first and second sides, the first side being coupled to the emitter electrode of said transistor and the source providing a constant-voltage thereacross independent of applied current between the first and second sides, said constant-voltage source comprising a resistor and a diode serially connected together and an amplifier having an input and an output, said amplifier input being coupled to said diode, the output of said amplifier comprising one of said first and second sides of said constant-voltage source and the side of the diode which is opposite from said resistor comprising the other side of said constant-voltage source, the amplifier having a feedback circuit from output to input enabling said amplifier to produce across the first and second sides of said constant-voltage source a constant-voltage ouput corresponding to the signal across said diode; b. current controlling photosensitive means having first and second sides, the first side being coupled to the collector electrode of said transistor of the first circuit section for controlling the amount of current therethrough corresponding to the intensity of received light; c. a bias circuit responsive to the current from said photosensitive means for applying a corresponding bias current to the base electrodes of both transistors in both said circuit sections, causing a voltage from base to emitter electrodes of the transistor in said first section which corresponds to intensity of the received light; d. a capacitor having first and second sides, the first side being coupled to the collector electrode of the transistor in the second circuit section enabling such transistor to provide a constant-current charge to the capacitor; and e. means for providing a source of potential across the second sides of said photosensitive means and said constant-voltage source of said first circuit section and a source of potential across said second sides of said capacitor and constant-voltage source of said second circuit section; f. the constant-voltage source of at least one of the first and second circuit sections comprising controllable means for adjusting the constant-voltage proportional to the logarithmic compression of a photographic exposure determining factor.

Claim 13

An electric shutter control circuit for a single lens reflex camera comprising: a. first and second mutually independent circuit sections, each comprising a transistor, and a constant-voltage source having first and second sides, the first side being coupled to the emitter electrode of said transistor and the source providing a constant-voltage thereacross independent of applied current between the first and second sides, said constant-voltage source comprising a resistor and a diode serially connected together and an amplifier having an input and an output, said amplifier input being coupled to said diode, the output of said amplifier comprising one of said first and second sides of said constant-voltage source and the side of the diode which is opposite from said resistor comprising the other side of said constant-voltage source, the amplifier having a feedback circuit from output to input enabling said amplifier to produce across the first and second sides of said constant-voltage source a constant-voltage ouput corresponding to the signal across said diode; b. current controlling photosensitive means having first and second sides, the first side being coupled to the collector electrode of said transistor of the first circuit section for controlling the amount of current therethrough corresponding to the intensity of received light; c. a bias circuit responsive to the current from said photosensitive means for applying a corresponding bias current to the base electrodes of both transistors in both said circuit sections, causing a voltage from base to emitter electrodes of the transistor in said first section which corresponds to intensity of the received light; d. a capacitor having first and second sides, the first side being coupled to the collector electrode of the transistor in the second circuit section enabling such transistor to provide a constant-current charge to the capacitor; and e. means for providing a source of potential across the second sides of said photosensitive means and said constant-voltage source of said first circuit section and a source of potential across said second sides of said capacitor and constant-voltage source of said second circuit section; f. the constant-voltage source of at least one of the first and second circuit sections comprising controllable means for adjusting the constant-voltage proportional to the logarithmic compression of a photographic exposure determining factor.