US4789777A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Photelectric amplifier having plural actuable feedback paths
Assignee: Pentax Corp
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Filing: 1987-06-24
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Granted: 1988-12-06
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Expires: 2007-06-24
Abstract
Abstract A photoelectric amplifier in a camera exposure system, in which a photodiode is connected across the inputs of an operational amplifier and charges an integrating circuit in a feedback path across the operational amplifier. The resistance of the feedback path can be varied in response to the film sensitivity. The output of the operational amplifier is compared against a films speed reference voltage. Thereby, a reduced range of film speed reference voltages need to be provided because of the optional gain of the photovoltage.
Inventors
- 👤 Satoshi Takami
- 👤 Yutaka Ohsawa
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 21:12
CPC Classifications
H; H10; H10F; H10F77/00; H10F77/95; H10F77/953; G; G03; G03B; G03B7/00; G03B7/24
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
145 words
A photoelectric amplifier comprising: a photosensitive element; an operational amplifier receiving an output of said photosensitive element; integrating means having a first terminal connected to said photosensitive element and being charged by said photosensitive element; a first electrical path connecting a second terminal of said integrating means to a non-inverting input terminal of said operational amplifier through a first resistance; an actuable second electrical path connecting an output terminal of said operational amplifier to said second terminal of said integrating means; an actuable third electrical path connecting said output terminal of said operational amplifier to an inverting input terminal of said operational amplifier; selecting means for selectively actuating said second and third paths, an integration voltage based on an input offset voltage of said operational amplifier being stored in said integrating means as an output of said operational amplifier when said third path is actuated.
Claim 2
Dependent Claim
145 words
A photoelectric amplifier comprising: a photosensitive element; an operational amplifier receiving an output of said photosensitive element; integrating means having a first terminal connected to said photosensitive element and being charged by said photosensitive element; a first electrical path connecting a second terminal of said integrating means to a non-inverting input terminal of said operational amplifier through a first resistance; an actuable second electrical path connecting an output terminal of said operational amplifier to said second terminal of said integrating means; an actuable third electrical path connecting said output terminal of said operational amplifier to an inverting input terminal of said operational amplifier; selecting means for selectively actuating said second and third paths, an integration voltage based on an input offset voltage of said operational amplifier being stored in said integrating means as an output of said operational amplifier when said third path is actuated.
Claim 3
Dependent Claim
57 words
A photoelectric amplifier of claim 1, further comprising: at least one fourth electrical path connecting said second terminal of said integrating means to said output terminal of said operational amplifier and having a resistance wherein said selecting means actuates one of said second, third and fourth switch a gain of said operational amplifier with said first resistance.
Claim 4
Dependent Claim
27 words
A photoelectric amplifier of claim 2, wherein said selecting means selects one of said second path and said fourth path in response to a film sensitivity value.
Claim 5
Dependent Claim
33 words
A photoelectric amplifier of claim 3, further comprising a comparator receiving an output of said operational amplifier and a reference voltage provided by said selecting means in response to said film sensitivity value.
Claim 6
Dependent Claim
14 words
A photoelectric amplifier of claim 1, wherein said operational amplifier comprises field effect transistors.
References Cited (Backward Citations)
US4216434A
Cited
US4426624A
Cited
US4508686A
Cited
US4439739A
Cited
US4459475A
Cited
US4626677A
Cited
US4673807A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-12-06 | 1992-06-06 | 1992-12-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-12-06 | 1996-06-06 | 1996-12-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-12-06 | 2000-06-06 | 2000-12-06 | $7700.00 | Window Closed / Lapsed |