Electric exposure control device

Claim 2

An electric exposure control device characterized by a photometric circuit including a photoelectric element and a first log-diode, a capacitor for storing the terminal voltage of the first log-diode, a differential amplifier, and a regenerator circuit comprising a transistor which operates in response to the output of the differential amplifier and including a second logdiode connected to the transistor, said differential amplifier comparing the terminal voltage of said capacitor with the terminal voltage of the second log-diode of the regenerator circuit so that the current which flows to the transistor in the regenerator circuit becomes responsive to a current in the photometric circuit, a transistor having an output resistance which is equal to the output resistance of the transistor in the regenerator circuit being used as a resistor element of a time constant circuit which controls the shutter speed.

Claim 3

An electric exposure control device according to claim 1, characterized in that a switch alternately connects a single diode which serves as both the log-diode in the photometric circuit and the log-diode in the regenerator circuit.

Claim 4

An electric exposure control device, comprising a photometric circuit having photosensitive means and a storage capacitor connectable to said photosensitive means for charging to a level indicative of the brightness sensed by said photosensitive means when connected to said photosensitive means, comparator means including a comparator circuit, said comparator circuit having an input connected with said capacitor and an output, said comparator means including a regenerator circuit connected to the output of said comparator circuit and connected with the other input of said comparator circuit to form an electrical feedback circuit, a timing circuit responsive to said comparator means and having a timing capacitor, a switching circuit having an input connected to and responsive to the timing capacitor for producing a signal controlling the duration during which a camera shutter is open, signal compreSsion means for logarithmically compressing signals applied thereto, and circuit means for coupling said compression means to said capacitor when said capacitor is connected to said photosensitive means and for coupling said compression means to said other input at other times.

Claim 5

An electric exposure control device, comprising a photometric circuit having photosensitive means and a storage capacitor connectable to said photosensitive means for charging to a level indicative of the brightness sensed by said photosensitive means when connected to said photosensitive means, comparator means including a comparator circuit, said comparator circuit having an input connected with said capacitor and an output, said comparator means including a regenerator circuit connected to the output of said comparator circuit and connected with the other input of said comparator circuit to form an electrical feedback circuit, a timing circuit responsive to said comparator means and having a timing capacitor, a switching circuit having an input connected to and responsive to the timing capacitor for producing a signal controlling the duration during which a camera shutter is open, signal compreSsion means for logarithmically compressing signals applied thereto, and circuit means for coupling said compression means to said capacitor when said capacitor is connected to said photosensitive means and for coupling said compression means to said other input at other times.

Claim 6

A device as in claim 3, wherein said timing circuit is responsive to said regenerator circuit.

Claim 7

A device as in claim 4, wherein said comparator circuit includes a pair of field effect transistors.

Claim 8

An electric exposure control device, comprising a photometric circuit having a photosensitive element and a logarithmic compression element connected to said photosensitive element for compressing voltages applied thereto, a differential amplifier circuit having a differential input connected to said compression element and being responsive to the voltage across said compression element, a regenerator circuit responsive to an output signal for said amplifier circuit, a controller circuit for controlling the exposure, and a network connecting the regenerator circuit to both the amplifier circuit and the controller circuit so as to deliver an output signal from the regenerator circuit to both the amplifier circuit and the controller circuit, whereby the output from the regenerator circuit is responsive to the output from the amplifier circuit, said regenerator circuit including a second logarithmic compression element, said amplifier circuit including a second differential input, said second compression element being connected to said second differential input for applying a compressed signal to said second differential input.

Claim 9

An electric exposure control device, comprising a photometric circuit having a photosensitive element and a logarithmic compression element connected to said photosensitive element for compressing voltages applied thereto, a differential amplifier circuit having a differential input connected to said compression element and being responsive to the voltage across said compression element, a regenerator circuit responsive to an output signal for said amplifier circuit, a controller circuit for controlling the exposure, and a network connecting the regenerator circuit to both the amplifier circuit and the controller circuit so as to deliver an output signal from the regenerator circuit to both the amplifier circuit and the controller circuit, whereby the output from the regenerator circuit is responsive to the output from the amplifier circuit, said regenerator circuit including a second logarithmic compression element, said amplifier circuit including a second differential input, said second compression element being connected to said second differential input for applying a compressed signal to said second differential input.

Claim 10

A device as in claim 6, further comprising a variable resistor, said regenerator circuit having an output circuit, and switch means for switching said variable resistor across said output circuit.

Claim 11

An electric exposure control device according to claim 6 which further comprises a memory capacitor and a memory switch between the photometric circuit and the differential amplifier circuit.

Claim 12

An electric exposure control device according to claim 6 in which said first element is a diode and said diode applies the compressed input to the differential amplifier circuit when the memory switch couples the photometric circuit with the memory capacitor.

Claim 13

An electric exposure control device according to claim 6 in which the regenerator circuit is composed of at least two transistors one of which is used for controlling the differential amplifier, and another of which is used for controlling the controller circuit.

Claim 14

An electric exposure control device according to claim 10 in which the controller circuit has a timer capacitor and a timer switch and controls the exposure time.

Claim 15

An electric exposure control device according to claim 11 in which the controller circuit comprises a Schmitt circuit with a field-effect transistor as its input-stage transistor.

Claim 16

An electric exposure control device according to claim 11 which further comprises a photo-sensitive element connected in parallel with the output circuit of the regenerator circuit.

Claim 17

An electric exposure control device according to claim 11 in which the differential amplifier circuit has a first potentiometer and the regenerator circuit has a second potentiometer, said first and second potentiometers are each set to to a given input value of.

Claim 18

An electric exposure control device according to claim 6 in which the output circuit of the differential amplifier circuit comprises compensator means for voltage changes due to thermal variation.

Claim 19

An electric exposure control device according to claim 6 which further comprises a main switch for power supply to the photometric circuit, and the differential amplifier circuit, and a secondary switch for power supply to the regenerator circuit and the controller circuit.

Claim 20

An electric exposure control device according to claim 16 in which the main switch is closed in association with camera release operation and the seCondary switch is self-held by the output of the controller circuit.

Claim 21

An electric exposure control device according to claim 17 in which the main switch is composed of two switches: one for activation of the device in association with camera release operation and the other for self-holding of the main switch in association with the secondary switch.

Claim 22

An electric exposure control device according to claim 16 which further comprises a diode which prohibits power supply to the regenerator circuit and the controller circuit through the main switch, but permitts power supply to the photometric circuit and the differential amplifier circuit through the secondary switch.

Claim 23

An electric exposure control device according to claim 6 which further comprises an ammeter as an indicator.

Claim 24

An electric exposure control device according to claim 6 wherein the controller circuit comprises at least two interchangeable variable elements, means for changing over the sensitivity of the photometric circuit is provided, and the interchange of said variable elements and the change-over of the sensitivity are simultaneously effected so as to widen the exposure range.

Claim 25

An electric exposure control device according to claim 21 wherein the variable elements are timer capacitors and the change-over means is a filter.

Claim 26

An electric exposure control device according to claim 21, which further comprises a secondary photosensitive means for automatically effecting the interchange and the change-over.

Claim 27

An automatic exposure control apparatus, comprising: photosensitive means for producing a variable electrical output in response to the brightness of light incident thereon; memory means for storing electrical values; switching means for coupling said photosensitive means at predetermined times and storing in said memory means a value determined at least partially by said photosensitive means; electrical comparison means having an output and having a first input coupled to said memory means and responsive to the value stored in said memory means, said electrical comparison means having a second input for producing an error signal at the output when the relationships between the inputs vary from each other; regenerative means coupling the output of said comparison means to the second input; shutter control means responsive to said switching means and coupled to the output for controlling a shutter on the basis of the output; compression means for logarithmically compressing electrical signals applied thereto; and circuit means for coupling said compression means to said memory means when the switching means couples said photosensitive means to said memory means so that the value stored in said memory means is modified by said compression means and for coupling said compression means to said second input of said comparison means so as to modify the value applied by said regenerative means to said second input.

Claim 28

An automatic exposure control apparatus, comprising: photosensitive means for producing a variable electrical output in response to the brightness of light incident thereon; memory means for storing electrical values; switching means for coupling said photosensitive means at predetermined times and storing in said memory means a value determined at least partially by said photosensitive means; electrical comparison means having an output and having a first input coupled to said memory means and responsive to the value stored in said memory means, said electrical comparison means having a second input for producing an error signal at the output when the relationships between the inputs vary from each other; regenerative means coupling the output of said comparison means to the second input; shutter control means responsive to said switching means and coupled to the output for controlling a shutter on the basis of the output; compression means for logarithmically compressing electrical signals applied thereto; and circuit means for coupling said compression means to said memory means when the switching means couples said photosensitive means to said memory means so that the value stored in said memory means is modified by said compression means and for coupling said compression means to said second input of said comparison means so as to modify the value applied by said regenerative means to said second input.

Claim 29

An apparatus as in claim 24, wherein: said compression means modifies the values at the second input in the same way as said compression means modifies the values across said memory means so that the error signal tends to drive the value at said second input to the value across said memory means and so that the output corresponds in value to signals applied to said memory means by said photosensitive means.

Claim 30

An apparatus as in claim 25, wherein said shutter control means includes: capacitive means; variable resistance means coupled to said capacitive means and coupled to the output of said comparison means so that its resistance varies in response to the output of said comparison means, said variable resistance means applying a voltage across said capacitive means; and trigger means coupled to said capacitive means and responsive to the voltage across said capacitive means for triggering when the voltage reaches a predetermined value.

Claim 31

An apparatus as in claim 24, wherein said shutter control means includes: capacitive means; variable resistance means coupled to said capacitive means and coupled to the output of said comparison means so that its resistance varies in response to the output of said comparison means, said variable resistance means applying a voltage across said capacitive means; and trigger means coupled to said capacitive means and responsive to the voltage across said capacitive means for triggering when the voltage reaches a predetermined value.

Claim 32

An automatic photoelectric exposure control device for a camera having an electronic shutter whose exposure time is controlled in accordance with the light intensity of the object to be photographed, comprising: a measuring circuit including photosensitive means arranged to receive light passing through a camera lens; a memory circuit including a capacitor for memorizing a value indicative of the light of said photosensitive means; a switch connecting and disconnecting the measuring circuit from said memory circuit; a differential amplifier having two differential inputs, one of said inputs being connected to said capacitor, said amplifier having an output; a regenerator circuit coupling the output to the other input of said differential amplifier circuit and having variable resistance means responsive to the output of said differential amplifier circuit; a shutter controlling circuit for controlling a shutter time, comprising a timing capacitor connected to said variable resistance means, and a switching circuit having an input connected to the capacitor, said capacitor having a voltage determined by said variable resistive means, said switching circuit defining the shutter opening interval on the basis of the voltage across said timing capacitor reaching a threshhold level so as to close the shutter; compression means for logarithmetically compressing electrical signals applied thereto; and circuit means for coupling said compression means to said memory circuit when said switch connects the measuring circuit with said memory circuit so as to modify the value memorized from the output of said photosensitive means, and for connecting said compression means to said other input of said differential amplifier and said regenerator circuit so as to modify the signal applied by said regenerator circuit to the other input.

Claim 33

An automatic photoelectric exposure control device for a camera having an electronic shutter whose exposure time is controlled in accordance with the light intensity of the object to be photographed, comprising: a measuring circuit including photosensitive means arranged to receive light passing through a camera lens; a memory circuit including a capacitor for memorizing a value indicative of the light of said photosensitive means; a switch connecting and disconnecting the measuring circuit from said memory circuit; a differential amplifier having two differential inputs, one of said inputs being connected to said capacitor, said amplifier having an output; a regenerator circuit coupling the output to the other input of said differential amplifier circuit and having variable resistance means responsive to the output of said differential amplifier circuit; a shutter controlling circuit for controlling a shutter time, comprising a timing capacitor connected to said variable resistance means, and a switching circuit having an input connected to the capacitor, said capacitor having a voltage determined by said variable resistive means, said switching circuit defining the shutter opening interval on the basis of the voltage across said timing capacitor reaching a threshhold level so as to close the shutter; compression means for logarithmetically compressing electrical signals applied thereto; and circuit means for coupling said compression means to said memory circuit when said switch connects the measuring circuit with said memory circuit so as to modify the value memorized from the output of said photosensitive means, and for connecting said compression means to said other input of said differential amplifier and said regenerator circuit so as to modify the signal applied by said regenerator circuit to the other input.

Claim 34

A device as in claim 28, wherein: said compression means includes a first compression element connected to said photosensitive means and a second compression element connected to the other input of said differential amplifier.

Claim 35

An apparatus as in claim 28, wherein said compression element includes: a compression element; and said circuit means includes switch means for switching said compression element into connection with said photosensitive means when said measuring means is connected to said memory means and for switching said compression elements into connection with the other input of said differential amplifier.

Claim 36

A device as in claim 28, wherein: said differential amplifier includes two field effect transistors, each gate of one of said transistors forming one of said two inputs.

Claim 37

A device as in claim 28, wherein: said regenerator circuit includes a first transistor whose base electrode is connected to the output of said differential amplifier and having an output electrode, a second transistor whose base electrode is connected to the output electrode of said first transistor and whose output electrode is connected to the other input of said differential amplifier; said variable resistance means in said regenerator circuit including a third transistor having a base electrode connected to the output of said differential amplifier and an output electrode connected to said timing capacitor.

Claim 38

A device as in claim 28, wherein: said regenerator circuit includes two transistors and a switchover switch; one of said transistors including a base elEctrode connected with the output of said differential amplifier and an output electrode connected to the base electrode of the other transistor, said other transistor forming a part of said variable resistance means; said second transistor having an output electrode connected to said timing capacitor through said switchover switch; said switchover switch alternately and selectively connecting the output electrode with the input of said differential amplifier and said timing capacitor.