Patent US1432928A successfully refreshed from Google Patents.
Patent US3877039A successfully refreshed from Google Patents.
US3877039A
Expired / Lapsed
US
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Exposure control system for cameras
Assignee: Panasonic Holdings Corp
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Filing: 1972-11-20
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Granted: 1975-04-08
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Expires: 1992-11-20
Abstract
Abstract An exposure control system for use with single lens reflex cameras in which a photo-diode is connected across first and second inputs of a differential amplifier, and first and second variable resistors are connected at one end to the first and second differential amplifier inputs, respectively, and at the other ends in common with a power source, the resistors being variable as a function of film speed adjustment and lens aperture adjustment, respectively, the output of the differential amplifier being negatively fed back to one of its inputs such that the amplification factor of the photo-current generated by the photo-diode is the ratio of the first and second resistors.
Inventors
- 👤 Eisuke Ichinohe
- 👤 Masaya Shimomura
- 👤 Yuji Tsuda
- 👤 Junji Kajiwara
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 12:05
CPC Classifications
G; G03; G03B; G03B7/00; G03B7/08; G03B7/081; G03B7/083
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
140 words
An exposure control system for use in a photographic camera, comprising: differential amplifier means having first and second inputs; a photoelectric transducer coupled across said first and second inputs; first impedance means coupled between said first input and an electrical supply source; second impedance means coupled between said second input and said supply source; means coupling an output of said differential amplifier means to one of said first and second inputs to negatively feed back a portion of the output signal from said amplifier means to said one input such that a photocurrent generated by said photoelectric transducer is amplified by the ratio of said first and second impedances; and means coupling said differential amplifier means to exposure control means of said camera to control the operation of the camera shutter as a function of the amplitude of said photocurrent.
Claim 2
Dependent Claim
140 words
An exposure control system for use in a photographic camera, comprising: differential amplifier means having first and second inputs; a photoelectric transducer coupled across said first and second inputs; first impedance means coupled between said first input and an electrical supply source; second impedance means coupled between said second input and said supply source; means coupling an output of said differential amplifier means to one of said first and second inputs to negatively feed back a portion of the output signal from said amplifier means to said one input such that a photocurrent generated by said photoelectric transducer is amplified by the ratio of said first and second impedances; and means coupling said differential amplifier means to exposure control means of said camera to control the operation of the camera shutter as a function of the amplitude of said photocurrent.
Claim 3
Dependent Claim
35 words
An exposure control system as defined in claim 1, further comprising storage means coupled to the output of said differential amplifier means for storing an electrical signal representing the photocurrent generated by said photoelectric transducer.
Claim 4
Dependent Claim
74 words
An exposure control system as defined in claim 2, further comprising: a constant current source coupled to said storage means for producing a signal having a constant current characteristic; a time integrating circuit coupled to said constant current source; and means coupling said time integrating circuit to said exposure control means to control the closing of the shutter of said camera as a function of the rate of integration of said time integrating circuit.
Claim 5
Dependent Claim
44 words
An exposure control system as defined in claim 3, wherein said storage means comprises first capacitance means coupled to an input of said constant current source and said time integrating circuit comprises second capacitance means coupled to an output of said constant current source.
Claim 6
Dependent Claim
40 words
An exposure control system as defined in claim 3, wherein an output of said constant current source is coupled to said one input of said differential amplifier means to feed back said constant current signal to said differential amplifier means.
Claim 7
Dependent Claim
38 words
An exposure control system as defined in claim 5, further comprising means to switch the output of said constant current source between said one input of said differential amplifier means and the input of said time integrating circuit.
Claim 8
Dependent Claim
64 words
An exposure control system as defined in claim 1, further comprising: a transistor coupled to one output of said differential amplifier means; and a diode coupled to a second output of said differential amplifier means, said diode being connected across the base and emitter electrodes of said transistor; wherein said one output of said differential amplifier means is coupled to said negative feedback means.
Claim 9
Dependent Claim
29 words
An exposure control system as defined in claim 1, wherein said first impedance means comprises a variable resistance element coupled to the lens aperture setting mechanism of the camera.
Claim 10
Dependent Claim
29 words
An exposure control system as defined in claim 8, wherein said second impedance means comprises a variable resistance element coupled to the film speed setting mechanism of the camera.
Claim 11
Dependent Claim
72 words
An exposure control system as defined in claim 1, further comprising: a first transistor having its input coupled to the output of said differential amplifier means; a second transistor having its input coupled to the output of said first transistor and its output coupled to said exposure control means; and a constant current source coupled to the junction between the output of said first transistor and the input of said second transistor.
Claim 12
Dependent Claim
81 words
The exposure control system as defined in claim 1, further comprising: a first transistor having its base electrode coupled to the output of said differential amplifier means and its output coupled to said exposure control means; a second transistor having its base electrode coupled in common with the base electrode of said first transistor; a resistance element coupled between the respective emitter electrodes of said first and second transistors; and an indicating means coupled to the output of said second transistor.
Claim 13
Dependent Claim
125 words
The exposure control system as defined in claim 1, further comprising: a first transistor having its base electrode coupled to the output of said differential amplifier means and its output coupled to said exposure control means; a second transistor having its base electrode coupled in common with the base electrode of said first transistor; a first diode coupled to the output of said second transistor; a field effect transistor having its gate electrode coupled to the junction between said first diode and the output of said second transistor; a second diode coupled to the source electrode of said field effect transistor; and wherein a constant current is supplied to one of said diodes and a logarithmically compressed variable current is supplied to the other diode.
Claim 14
Dependent Claim
32 words
The exposure control system as defined in claim 12, further comprising indicating means coupled to the output of said field transistor, said indicating means being driven by said logarithmically compressed variable current.
Claim 15
Dependent Claim
51 words
An exposure control system as defined in claim 1, further comprising: a constant current source coupled to said transducer; and a storage capacitor coupled betwen control terminals of a high input impedance amplifier constituting a portion of said amplifier means for storing a signal representing the photocurrent generated by said transducer.
Claim 16
Dependent Claim
75 words
An exposure control system as defined in claim 1, wherein said means coupling said amplifier means to said exposure control means comprises an exposure time conversion circuit including a time integrating capacitor, a trigger switch coupled in parallel with said capacitor, and a control switch coupled to said capacitor and having a first contact coupled to an output of said amplifier means and a second contact coupled to said supply source through a resistance element.
Claim 17
Dependent Claim
134 words
An exposure control system as defined in claim 1, further comprising a flash bulb discharge circuit including a time-integrating capacitor, a trigger switch coupled in parallel with said capacitor, a high input impedance circuit adapted to be triggered by the charging or discharging current of said capacitor, and a control switch coupled in series between said capacitor and the input of said high input impedance circuit, the opening of said control switch being controlled by movement of the shutter release mechanism of said camera in a first direction, said trigger switch being opened after said control switch is opened, said capacitor being charged or discharged when said control switch is closed by movement of said shutter release mechanism in a second direction after the shutter of said camera and said trigger switch are opened.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-04-07 | 1978-10-07 | 1979-04-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-04-07 | 1982-10-07 | 1983-04-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-04-07 | 1986-10-07 | 1987-04-08 | $7700.00 | Window Closed / Lapsed |