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 Title: |
US3871020:
CHROMINANCE SIGNAL CORRECTION
[ Derwent Title ]
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| Country: |
US United States of America
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| Inventor: |
Wilber, James Albert; Indianapolis, IN
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| Assignee: |
RCA Corporation, New York, NY
other patents from RCA CORPORATION (466175) (approx. 7,929)
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| Published / Filed: |
1975-03-11
/ 1973-05-07
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| Application Number: |
US1973000357564
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| IPC Code: |
Advanced:
H04N 9/85;
Core:
H04N 9/82;
IPC-7:
H04N 5/76;
H04N 9/02;
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| U.S. Class: |
Current:
386/013;
386/045;
386/E09.044;
Original:
358/008;
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| Field of Search: |
178/5.4 R,5.4 CD,5.4 SY
358/008
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| Priority Number: |
| 1973-05-07 |
US1973000357564 |
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| Abstract: |
In a video disc player, a recorded composite signal, recovered during disc playback, includes a chrominance signal component buried in the midband of the accompanying luminance signal component. The player includes video processing circuits converting the recovered signal to an output composite signal in which the chrominance signal component occupies a higher frequency band, and employing the step of heterodyning the recovered composite signal with oscillations at a nominal frequency of fs + fs ' (where fs is the color subcarrier frequency of the output, and fs ' is the buried color subcarrier frequency of the disc signal). To stabilize the output chrominance signal component against spurious frequency variations accompanying disc playback, a phase locked loop (PLL) system is established to cause the fs + fs ' oscillations to track the disc frequency variations. The PLL system employs a voltage controlled oscillator (VCO) operating at a nominal frequency of 1/2 fs - fs ', and responding to the output of a phase detector, comparing the synchronizing burst component of the output chrominance signal with the highly stable output of a reference oscillator operating at fs. The VCO output is heterodyned with oscillations at 3/2 fs, derived from the reference oscillator, to provide the desired oscillation output varying about fs + fs '. "Sidelock" under disc playback initiation conditions is avoided by limiting the hold-in range of the VCO. A sweep voltage input to the VCO is supplied under out-of-lock conditions to enable phase lock acquisition. Upon achievement of phase lock, sweep generation is disabled, and sweep voltage sweeps back to mid-range value with normal slope. Sample-and-hold circuitry is employed in error voltage development, to enable PLL system to hold within rapid pull-in range during lengthy signal dropouts.
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| Attorney, Agent or Firm: |
Whitacre, E. M. ;
Meagher, William H. ;
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| Primary / Asst. Examiners: |
Murray, Richard;
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| INPADOC Legal Status: |
None
Family Legal Status Report
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| Family: |
Show 15 known family members
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First Claim:
Show all 8 claims |
What is claimed is:
1. In a video disc player including (a) video disc playback apparatus for developing a composite color television signal including a chrominance signal component occupying a first band of frequencies and comprising sidebands of a color subcarrier at a nominal frequency of fs ' and an accompanying color synchronizing component comprising recurring bursts of oscillations at said nominal frequency of fs ' said components however being subject to spurious frequency variations; and (b) means for deriving from said developed composite color television signal a chrominance signal component occupying a second band of frequencies, separate from and higher than said first band, and comprising sidebands of a color subcarrier at a nominal frequency of fs and an accompanying color synchronizing component comprising recurring bursts of oscillations at said nominal frequency of fs ' said deriving means including a modulator responsive to the composite signal developed by said playback apparatus and to additional oscillations; apparatus for rendering the frequencies of said derived signal components substantially independent of said spurious frequency variations, comprising the combination of:
- a crystal controlled oscillator operating at the frequency fs ;
- a voltage controlled oscillator having a nominal operating frequency appreciably less than either fs or fs ', but subject to variation within a third frequency band, separate from and lower than said first band, in accordance with a control voltage input;
- phase detector means responsive to the output of said crystal controlled oscillator and to the color synchronizing component of said derived signal;
- means for deriving said control voltage input from said phase detector means;
- means for effectively frequency multiplying the output of said crystal controlled oscillator;
- means for heterodyning the output of said frequency multiplying means with the output of said voltage controlled oscillator;
- and means for utilizing the output of said heterodyning means as said additional oscillations to which said modulator is responsive.
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| Background / Summary: |
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| Drawing Descriptions: |
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| Description: |
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| Forward References: |
Show 8 U.S. patent(s) that reference this one
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