US3602641A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Dark current compensation circuit
Assignee: US Philips Corp
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Filing: 1969-09-24
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Granted: 1971-08-31
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Expires: 1989-09-24
Abstract
Abstract A dark current compensation circuit for a television camera features a switch for controlling an X-ray tube located in front of the camera, a video amplifier is coupled to the camera and a peak rectifier circuit is in turn coupled to the amplifier output. A switch synchronized with the first switch connects the rectifier to a capacitor to establish a dark current bias voltage which is applied to the amplifier.
Inventors
- 👤 Tom Heise
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 01:37
CPC Classifications
H; H04; H04N; H04N23/00; H04N23/80; H04N23/81; H04N5/00; H04N5/30; H04N5/32
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
155 words
A circuit for eliminating dark current effects of a television camera tube, comprising circuit means for alternately causing video signals and dark current signals to be provided by said tube; a video amplifier having a signal input coupled to said tube, a bias input, and an output; a peak rectifier circuit coupled to said amplifier output; a storage circuit coupled to said bias input; a first switch coupled intermediate said rectifier circuit and said storage circuit; said first switch being controlled by said circuit means to connect said rectifier circuit to said storage circuit only during the occurrence of said dark current signal and to disconnect said rectifier circuit from said storage circuit during the occurrence of said video signals, said circuit means comprising time-delay means to reconnect the rectifier and storage circuits through said first switch only after a time delay of at least one frame period from the cessation of said video signals.
Claim 2
Dependent Claim
155 words
A circuit for eliminating dark current effects of a television camera tube, comprising circuit means for alternately causing video signals and dark current signals to be provided by said tube; a video amplifier having a signal input coupled to said tube, a bias input, and an output; a peak rectifier circuit coupled to said amplifier output; a storage circuit coupled to said bias input; a first switch coupled intermediate said rectifier circuit and said storage circuit; said first switch being controlled by said circuit means to connect said rectifier circuit to said storage circuit only during the occurrence of said dark current signal and to disconnect said rectifier circuit from said storage circuit during the occurrence of said video signals, said circuit means comprising time-delay means to reconnect the rectifier and storage circuits through said first switch only after a time delay of at least one frame period from the cessation of said video signals.
Claim 3
Dependent Claim
36 words
A circuit as claimed in claim 1 wherein said storage circuit comprises a controlled element having an output electrode coupled to said amplifier and a control electrode; and a first capacitor coupled to said control electrode.
Claim 4
Dependent Claim
30 words
A circuit as claimed in claim 2 wherein said peak rectifier circuit comprises a second capacitor having a capacitance substantially equal to 10 times the capacitance of said first capacitor.
Claim 5
Dependent Claim
48 words
A circuit as claimed in claim 1 further comprising means for generating line-blanking pulses; a gate comprising a controlled element having an input electrode coupled to said generating means, and an output electrode coupled to said amplifier bias input, and a control electrode coupled to said storage circuit.
Claim 6
Dependent Claim
32 words
A circuit as claimed in claim 1 wherein said circuit means further comprises an X-ray tube disposed to irradiate said television camera tube, and a second switch coupled to said X-ray tube.
Claim 7
Dependent Claim
17 words
A circuit as claimed in claim 1 wherein said time delay comprises at least two field periods.
Claim 8
Dependent Claim
14 words
A circuit as claimed in claim 1 wherein said tube comprises a photosemiconductive tube.
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) | 1974-08-30 | 1975-03-01 | 1975-08-31 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-08-30 | 1979-03-01 | 1979-08-31 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-08-30 | 1983-03-01 | 1983-08-31 | $7700.00 | Window Closed / Lapsed |