US3699241A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Color television system with automatic correction of chroma amplitudes
Assignee: AT&T Inc
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Filing: 1971-01-06
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Granted: 1972-10-17
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Expires: 1991-01-06
Abstract
Abstract The low frequency portion of a color camera output signal is monitored and used to correct the carrier-borne color components of the composite output. The inherent redundancy of four independent video components provides the monitoring capability. A suggested embodiment utilizes a true low frequency luminance signal and the three carrier-borne color components (preferably red, green and blue). These components are detected and the resulting baseband signals are combined to yield a derived luminance signal. Comparison of the true and derived luminance produces a control signal which is fed back to vary the common factor by which all of the color components are amplified. In this manner compensation is provided for degradation of the carrier frequency (color) components, such as may be caused by loss of resolution of the camera tube or high frequency roll-off of a transmission link.
Inventors
- 👤 Arthur Bertel Larsen
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 07:37
CPC Classifications
H; H04; H04N; H04N23/00; H04N23/10; H04N23/12; H04N9/00; H04N9/64; H04N9/68
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
137 words
A color transmission system of the type having camera means for producing four independent video components, one of said components containing true luminance information and the other three of said components containing color information, CHARACTERIZED IN THAT, said system further includes a feedback correction circuit for automatically adjusting the amplitudes of the chroma components, said circuit comprising: means for monitoring the luminance component, means for monitoring the chroma components, means for combining the chroma components to form a representative luminance signal derived exclusively from said chroma components, means for amplifYing each of said chroma components by a common variable gain factor, and feedback means for comparing the true luminance component and the representative luminance signal and controlling said variable gain factor so that the amplitudes of the true luminance component and the representative luminance signal are equalized.
Claim 2
Dependent Claim
137 words
A color transmission system of the type having camera means for producing four independent video components, one of said components containing true luminance information and the other three of said components containing color information, CHARACTERIZED IN THAT, said system further includes a feedback correction circuit for automatically adjusting the amplitudes of the chroma components, said circuit comprising: means for monitoring the luminance component, means for monitoring the chroma components, means for combining the chroma components to form a representative luminance signal derived exclusively from said chroma components, means for amplifYing each of said chroma components by a common variable gain factor, and feedback means for comparing the true luminance component and the representative luminance signal and controlling said variable gain factor so that the amplitudes of the true luminance component and the representative luminance signal are equalized.
Claim 3
Dependent Claim
157 words
A television system of the type having a single pickup tube; camera for generating a video output having a plurality of components including a low frequency luminance signal representative of the brightness of a scene and at least three modulated color carriers, the modulation on each carrier representing the amplitude of light from said scene within one region of the visible spectrum, and means for transmitting said plurality of video components, CHARACTERIZED IN THAT said transmitting means includes means for forming from said modulated color carriers color signals representative of the color content of said scene, means for deriving exclusively from said modulated color carriers a derived luminance signal, means for comparing the amplitudes of said derived luminance signal and said low frequency luminance signal, and means responsive to said comparison for controlling the gain factor by which each of said color signals is amplified to equalize the amplitudes of the derived and low frequency luminance signals.
Claim 4
Dependent Claim
157 words
A television system of the type having a single pickup tube; camera for generating a video output having a plurality of components including a low frequency luminance signal representative of the brightness of a scene and at least three modulated color carriers, the modulation on each carrier representing the amplitude of light from said scene within one region of the visible spectrum, and means for transmitting said plurality of video components, CHARACTERIZED IN THAT said transmitting means includes means for forming from said modulated color carriers color signals representative of the color content of said scene, means for deriving exclusively from said modulated color carriers a derived luminance signal, means for comparing the amplitudes of said derived luminance signal and said low frequency luminance signal, and means responsive to said comparison for controlling the gain factor by which each of said color signals is amplified to equalize the amplitudes of the derived and low frequency luminance signals.
Claim 5
Dependent Claim
136 words
A television system comprising, a camera having a single pickup tube for generating a video output having a low frequency signal representing the intensity of the scene being televised and a plurality of modulated color carriers, each carrier containing different color information of said scene, means for detecting each of said modulated color carriers to form from each a baseband color signal, means for combining said baseband signals to form a derived luminance signal, means for comparing said low frequency signal and said derived luminance signal to form an error signal representative of the difference between said signals, and means for amplifying exclusively each of said baseband color signals by a common gain factor to equalize the amplitudes of said low frequency signal and said derived luminance signal, said factor being controlled by said error signal.
Claim 6
Dependent Claim
136 words
A television system comprising, a camera having a single pickup tube for generating a video output having a low frequency signal representing the intensity of the scene being televised and a plurality of modulated color carriers, each carrier containing different color information of said scene, means for detecting each of said modulated color carriers to form from each a baseband color signal, means for combining said baseband signals to form a derived luminance signal, means for comparing said low frequency signal and said derived luminance signal to form an error signal representative of the difference between said signals, and means for amplifying exclusively each of said baseband color signals by a common gain factor to equalize the amplitudes of said low frequency signal and said derived luminance signal, said factor being controlled by said error signal.
Claim 7
Dependent Claim
27 words
A television system as claimed in claim 3 wherein said plurality of modulated color carriers include three signals, each representing one primary color image of said scene.
Claim 8
Dependent Claim
36 words
A television system as claimed in claim 3 wherein said baseband signals represent red, green and blue color images of said scene, and said combining means sums said baseband signals to form the derived luminance signal.
Claim 9
Dependent Claim
34 words
A television system as claimed in claim 3 wherein at least two of said plurality of modulated color carriers are frequency interleaved and at a frequency above the frequency of said low frequency signal.
Claim 10
Dependent Claim
35 words
A television system as claimed in claim 3 wherein said means for amplifying each of said baseband color signals is a variable gain amplifier for adjusting the gain of the plurality of modulated color carriers.
Claim 11
Dependent Claim
24 words
A television system as claimed in claim 7 wherein said modulated color carriers are transmitted in a single channel containing said variable gain amplifier.
Claim 12
Dependent Claim
30 words
A television system as claimed in claim 3 wherein at least two of said plurality of modulated carriers occupy separated frequency bands above the frequency of said low frequency signal.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-10-17 | 1976-04-17 | 1976-10-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-10-17 | 1980-04-17 | 1980-10-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-10-17 | 1984-04-17 | 1984-10-17 | $7700.00 | Window Closed / Lapsed |