US3812504A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Indicator arrangement for a photographic camera
Assignee: Agfa Gevaert AG
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Filing: 1973-04-12
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Granted: 1974-05-21
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Expires: 1993-04-12
Abstract
Abstract The battery of the camera has a voltage divider including a photoelectric transducer connected in parallel with it. The voltage divider tap is connected to the base of a transistor whose collector-emitter circuit is connected to a luminescent diode through a series resistor. The transistor is highly conductive when insufficient light for an exposure falls on the photoelectric transducer. Further, a variable resistor in parallel with the luminescent diode is adjusted so that the voltage drop across the luminescent diode is less than its threshold voltage for a battery voltage less than a predetermined minimum battery voltage when light is blocked from the photoelectric transducer.
Inventors
- 👤 E Wagensonner
- 👤 K Borowski
- 👤 F Stumpf
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 14:26
CPC Classifications
G; G03; G03B; G03B7/00; G03B7/08; G03B7/081; G03B7/083
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
223 words
In a camera having a battery for furnishing a battery voltage, an arrangement for furnishing a visual indication when the light available for an exposure is less than a predetermined light quantity and when said battery voltage exceeds a predetermined minimum battery voltage, comprising, in combination, light source means connected to said battery for emitting light when the voltage across said light source means exceeds a predetermined threshold voltage; transistor means having an emitter-collector circuit connected to said light source means, and a base; voltage divider means connected to said battery and having a voltage divider tap connected to said base of said transistor means, said voltage divider means having light-sensitive transducer means connected to said base of said transistor means in such a manner that said emitter-collector circuit is conductive when said light available for an exposure is less than said predetermined light quantity; and resistance means connected to said emitter-collector circuit and to said light source means in such a manner that said voltage across said light source means exceeds said predetermined threshold voltage when no light falls on said light-sensitive transducer means and said battery voltage exceeds said predetermined minimum battery voltage, and is less than said threshold voltage when no light falls on said light-sensitive transducer means and said battery voltage is less than said predetermined minimum battery voltage.
Claim 2
Dependent Claim
223 words
In a camera having a battery for furnishing a battery voltage, an arrangement for furnishing a visual indication when the light available for an exposure is less than a predetermined light quantity and when said battery voltage exceeds a predetermined minimum battery voltage, comprising, in combination, light source means connected to said battery for emitting light when the voltage across said light source means exceeds a predetermined threshold voltage; transistor means having an emitter-collector circuit connected to said light source means, and a base; voltage divider means connected to said battery and having a voltage divider tap connected to said base of said transistor means, said voltage divider means having light-sensitive transducer means connected to said base of said transistor means in such a manner that said emitter-collector circuit is conductive when said light available for an exposure is less than said predetermined light quantity; and resistance means connected to said emitter-collector circuit and to said light source means in such a manner that said voltage across said light source means exceeds said predetermined threshold voltage when no light falls on said light-sensitive transducer means and said battery voltage exceeds said predetermined minimum battery voltage, and is less than said threshold voltage when no light falls on said light-sensitive transducer means and said battery voltage is less than said predetermined minimum battery voltage.
Claim 3
Dependent Claim
23 words
An arrangement as set forth in claim 1, further comprising blocking means for blocking light from said light-sensitive transducer means upon external activation.
Claim 4
Dependent Claim
40 words
An arrangement as set forth in claim 1, wherein said resistance means comprise a variable resistor connected in parallel with said light source means, thereby forming a parallel circuit, and a fixed resistor connected in series with said parallel circuit.
Claim 5
Dependent Claim
17 words
An arrangement as set forth in claim 1, wherein said light source means is a luminescent diode.
Claim 6
Dependent Claim
48 words
An arrangement as set forth in claim 1, further comprising exposure control means connected to said indicator arrangement; and wherein said light-sensitive transducer means comprise a differential light-sensitive transducer having a first half connected to said indicator arrangement and a second half connected to said exposure control means.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-05-20 | 1977-11-19 | 1978-05-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-05-20 | 1981-11-19 | 1982-05-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-05-20 | 1985-11-19 | 1986-05-21 | $7700.00 | Window Closed / Lapsed |