Patent US3728476A successfully refreshed from Google Patents.
US3728476A
Expired / Lapsed
US
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Luminance notch filter
Assignee: General Electric Co
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Filing: 1971-03-17
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Granted: 1973-04-17
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Expires: 1991-03-17
Abstract
Abstract Chrominance frequency components in the luminance channel of a color television camera are reduced by a luminance channel notch filter having substantially linear phase characteristics and adjustable notch depth. The luminance notch is developed by subtraction of a bandpass-filtered video signal from the overall video input signal. The filter, which exhibits symmetrical transient response, improved low light level noise performance and minimizes spurious color effects due to interaction of chrominance signal components with the luminance signal.
Inventors
- 👤 W Bates
- 👤 T True
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 13:25
CPC Classifications
H; H03; H03H; H03H11/00; H03H11/02; H03H11/04; H03H11/12; H03H11/1217; H04; H04N; H04N9/00; H04N9/77; H04N9/78
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
154 words
A substantially symmetrical notch filter for rejecting a relatively narrow band of frequencies from a wide band luminance signal wherein said narrow band of frequencies has a width corresponding substantially to the band width of a chrominance signal, comprising: a delay line producing substantially linear changes in phase with frequency; a bandpass filter producing substantially linear changes in phase with frequency over said narrow band of frequencies corresponding substantially to the band width of a chrominance signal, said bandpass filter further producing substantially equal and opposite phase shifts for equal frequency deviations above and below a center-tuned frequency; means for coupling said wide band luminance signal to the input of each of said delay line and bandpass filter; and circuit means coupled to the output of said delay line and said bandpass filter for subtracting the relatively narrow band of frequencies passed by said bandpass filter from the signal passed by said delay line.
Claim 2
Dependent Claim
154 words
A substantially symmetrical notch filter for rejecting a relatively narrow band of frequencies from a wide band luminance signal wherein said narrow band of frequencies has a width corresponding substantially to the band width of a chrominance signal, comprising: a delay line producing substantially linear changes in phase with frequency; a bandpass filter producing substantially linear changes in phase with frequency over said narrow band of frequencies corresponding substantially to the band width of a chrominance signal, said bandpass filter further producing substantially equal and opposite phase shifts for equal frequency deviations above and below a center-tuned frequency; means for coupling said wide band luminance signal to the input of each of said delay line and bandpass filter; and circuit means coupled to the output of said delay line and said bandpass filter for subtracting the relatively narrow band of frequencies passed by said bandpass filter from the signal passed by said delay line.
Claim 3
Dependent Claim
118 words
The notch filter of claim 1 wherein said circuit means comprises: a differential amplifier having first and second inputs; means coupling the output of said delay line to said first input of said differential amplifier so as to produce a signal of predetermined phase angle for any given frequency, respectively, at said first input of said differential amplifier; and means coupling the output of said bandpass filter to the second input of said differential amplifier so as to produce a signal substantially of said predetermined phase angle for said given frequency, respectively, at said second input of said differential amplifier, said differential amplifier producing an output signal having reduced amplitude at the passband frequencies of said bandpass filter.
Claim 4
Dependent Claim
21 words
The notch filter of claim 1 including variable attenuating means coupling the output of said bandpass filter to said circuit means.
Claim 5
Dependent Claim
28 words
The notch filter of claim 2 wherein said means coupling the output of said bandpass filter to the second input of said differential amplifier comprises variable attenuating means.
Claim 6
Dependent Claim
22 words
The notch filter of claim 1 including an additional delay line coupling the output of said bandpass filter to said circuit means.
Claim 7
Dependent Claim
29 words
The notch filter of claim 2 wherein said means coupling the output of said bandpass filter to the second input of said differential amplifier comprises an additional delay line.
Claim 8
Dependent Claim
57 words
THe notch filter of claim 2 wherein said means coupling the output of said bandpass filter to the second input of said differential amplifier comprises an additional delay line coupled to said second input of said differential amplifier, and variable attenuating means coupling the output of said bandpass filter to the input of said additional delay line.
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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) | 1976-04-16 | 1976-10-16 | 1977-04-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-04-16 | 1980-10-16 | 1981-04-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-04-16 | 1984-10-16 | 1985-04-17 | $7700.00 | Window Closed / Lapsed |