US3555181A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Automatic video level control employing iris and amplifier gain adjustments
Assignee: AT&T Inc
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Filing: 1968-06-05
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Granted: 1971-01-12
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Expires: 1988-06-05
Abstract
Abstract The amplitude of a signal generated by a video pickup tube is controlled by employing an automatic iris at high illumination levels and an automatic gain control circuit at low illumination levels. The crossover point between iris and gain control is selected so that the gain circuit operates as long as increased illumination and decreased gain improve the signal to noise ratio and picture quality. Above this point, signal level is maintained by an automatic iris which improves the depth of field as illumination increases. Both functions are controlled by sampling a selected field of the output from the pickup tube.
Inventors
- 👤 Werner Thommen
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 04:02
CPC Classifications
H; H04; H04N; H04N7/00; H04N7/14; H04N7/141; H04N23/00; H04N23/70; H04N23/72
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
117 words
In a video transmission system including video pickup means for converting the light image of a scene into electrical signals and means for amplifying said signals, an automatic video level control comprising: adjustable aperture means responsive to a first control signal for controlling the intensity of light from said scene which reaches said pickup means, a gain control circuit associated with said amplifying means and responsive to a second control signal, and control means responsive to a sample of said amplified electrical signals representative of a predetermined portion of said light image for developing said first control signal in a selected high illumination range And for developing said second control signal in a selected low illumination range.
Claim 2
Dependent Claim
117 words
In a video transmission system including video pickup means for converting the light image of a scene into electrical signals and means for amplifying said signals, an automatic video level control comprising: adjustable aperture means responsive to a first control signal for controlling the intensity of light from said scene which reaches said pickup means, a gain control circuit associated with said amplifying means and responsive to a second control signal, and control means responsive to a sample of said amplified electrical signals representative of a predetermined portion of said light image for developing said first control signal in a selected high illumination range And for developing said second control signal in a selected low illumination range.
Claim 3
Dependent Claim
48 words
An automatic video level control as defined in claim 1 wherein, said low illumination range extends from a selected low illumination to the illumination level at which additional illumination does not appreciably improve picture quality, and wherein the high illumination range is contiguous with the low illumination range.
Claim 4
Dependent Claim
38 words
An automatic video level control as defined in claim 2 wherein said low illumination range extends from a highlight luminance of 3 to 16 foot lamberts and said high illumination range extends from 16 to 1000 foot lamberts.
Claim 5
Dependent Claim
139 words
An automatic video signal amplitude control system comprising: a control circuit; an iris under control of signals from said control circuit; a video camera tube; a preamplifier supplied with signals from said video camera tube; a controlled variable gain amplifier supplied with signals from said preamplifier, the gain of said amplifier being under control of signals from said control circuit; a signal analyzer supplied with signals from said variable gain amplifier for disabling said control device at preselected times; and a comparator supplied with a control signal from said analyzer and with a reference signal for comparing said control signal with said reference signal and for supplying signals to said control circuit, said control circuit actuating said iris in a selected high illumination range and controlling said gain of said variable gain amplifier in a selected low illumination range.
Claim 6
Dependent Claim
139 words
An automatic video signal amplitude control system comprising: a control circuit; an iris under control of signals from said control circuit; a video camera tube; a preamplifier supplied with signals from said video camera tube; a controlled variable gain amplifier supplied with signals from said preamplifier, the gain of said amplifier being under control of signals from said control circuit; a signal analyzer supplied with signals from said variable gain amplifier for disabling said control device at preselected times; and a comparator supplied with a control signal from said analyzer and with a reference signal for comparing said control signal with said reference signal and for supplying signals to said control circuit, said control circuit actuating said iris in a selected high illumination range and controlling said gain of said variable gain amplifier in a selected low illumination range.
Claim 7
Dependent Claim
33 words
An automatic video signal amplitude control system, as defined in claim 4, wherein said signal analyzer disables said control device during the top one-quarter and during the bottom one-quarter of each video frame.
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) | 1974-01-11 | 1974-07-13 | 1975-01-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-01-11 | 1978-07-13 | 1979-01-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-01-11 | 1982-07-13 | 1983-01-12 | $7700.00 | Window Closed / Lapsed |