US3715474A
Expired / Lapsed
US
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Color video recording and playback system
Assignee: International Business Machines Corp
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Filing: 1967-12-26
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Granted: 1973-02-06
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Expires: 1987-12-26
Abstract
Abstract A color video recording and playback system employs a continuous sinusoidal subharmonic of the color subcarrier signal, which is used to amplitude modulate a frequency modulated video signal during the record mode, and is retrieved during playback for synchronization and phase correction of the color signal.
Inventors
- 👤 R Calfee
- 👤 E Hopner
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 22:00
CPC Classifications
H; H04; H04N; H04N9/00; H04N9/79; H04N9/87; H04N9/898
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
113 words
A color video recording system compatible with NTSC standards, comprising: means for frequency modulating a composite color video signal; means for providing a color subcarrier having a reference frequency and a continuous sinusoidal waveform; a frequency divider coupled to said color subcarrier providing means for producing a subharmonic frequency of said color sUbcarrier; an amplitude modulation circuit means coupled to the outputs of the frequency modulating means and said frequency divider, so that the subharmonic subcarrier is modulated with the frequency modulated video signal, thereby to provide an amplitude modulated FM signal substantially free of spurious amplitude variations; and head means for recording said amplitude modulated FM video signal on a storage medium.
Claim 2
Dependent Claim
113 words
A color video recording system compatible with NTSC standards, comprising: means for frequency modulating a composite color video signal; means for providing a color subcarrier having a reference frequency and a continuous sinusoidal waveform; a frequency divider coupled to said color subcarrier providing means for producing a subharmonic frequency of said color sUbcarrier; an amplitude modulation circuit means coupled to the outputs of the frequency modulating means and said frequency divider, so that the subharmonic subcarrier is modulated with the frequency modulated video signal, thereby to provide an amplitude modulated FM signal substantially free of spurious amplitude variations; and head means for recording said amplitude modulated FM video signal on a storage medium.
Claim 3
Dependent Claim
113 words
A color video recording system compatible with NTSC standards, comprising: means for frequency modulating a composite color video signal; means for providing a color subcarrier having a reference frequency and a continuous sinusoidal waveform; a frequency divider coupled to said color subcarrier providing means for producing a subharmonic frequency of said color sUbcarrier; an amplitude modulation circuit means coupled to the outputs of the frequency modulating means and said frequency divider, so that the subharmonic subcarrier is modulated with the frequency modulated video signal, thereby to provide an amplitude modulated FM signal substantially free of spurious amplitude variations; and head means for recording said amplitude modulated FM video signal on a storage medium.
Claim 4
Dependent Claim
113 words
A color video recording system compatible with NTSC standards, comprising: means for frequency modulating a composite color video signal; means for providing a color subcarrier having a reference frequency and a continuous sinusoidal waveform; a frequency divider coupled to said color subcarrier providing means for producing a subharmonic frequency of said color sUbcarrier; an amplitude modulation circuit means coupled to the outputs of the frequency modulating means and said frequency divider, so that the subharmonic subcarrier is modulated with the frequency modulated video signal, thereby to provide an amplitude modulated FM signal substantially free of spurious amplitude variations; and head means for recording said amplitude modulated FM video signal on a storage medium.
Claim 5
Dependent Claim
110 words
In combination with the color video recording system of claim 1, a system for producing a read out signal from said storage medium, said system including head means for reading out a recorded signal; a first signal channel having limiting means coupled to said head means for removing amplitude modulation from said read out signal, and means coupled to said limiting means for detecting the frequency modulation of said color video signal; a second signal channel including an amplitude modulation detection means for detecting the color subcarrier signal; and means coupled to said first and second channels for demodulating the color video signal in synchronization with the detected subcarrier signal.
Claim 6
Dependent Claim
64 words
The combination of a color video recording system and color video reproducing system of claim 2, wherein the second signal channel further includes a tuned circuit coupled to the output of the amplitude modulation detection means, and a means connected between said tuned circuit and said demodulating means for multiplying the detected subharmonic color subcarrier to produce the frequency of the color reference subcarrier.
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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) | 1976-02-06 | 1976-08-07 | 1977-02-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-02-06 | 1980-08-07 | 1981-02-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-02-06 | 1984-08-07 | 1985-02-06 | $7700.00 | Window Closed / Lapsed |