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US 4,376,956 AGranted
Video disc player having timebase correction and constant angular velocity turntable
AssigneeRCA Corporation
InventorKevin C. Kelleher
Life of this patent
Estimating the term…
Abstract
The burst component of a video signal recovered from a video disc record is applied to a timebase correction servo for controlling the tangential position of the player pick-up transducer in a sense to minimize timebase errors. The record is rotated at a constant angular velocity whereby, for a given displacement of the pick-up transducer, the servo loop gain tends to vary with the radial position of the transducer which, in turn, undesirably influences the servo sensitivity and dynamic stability. A loop gain compensator, responsive to a second component of the recovered video signal proportional to the playing time of the disc, regulates the servo gain at a substantially constant value thereby improving the loop stability and sensitivity.
Claims7
A video disc player, comprising, in combination:
- turntable means for rotating a video disc record at a predetermined substantially constant angular velocity;
- transducer means for recovering a recorded signal from said record;
- signal processing means responsive to a first component of the recovered signal for producing a timebase error correction signal;
- feedback means for applying said timebase error correction signal to said transducer means in a sense to minimize timebase errors of said recovered signal thereby forming a closed loop servo system, said system tending to exhibit a loop gain dependent upon the radial position of said transducer with respect to said record;
- and
- loop gain regulating means responsive to a second component of said recovered signal for regulating the loop gain of said closed loop servo system.
3 more elements
A video disc player, comprising:
- turntable means for rotating a video disc record at a predetermined substantially constant angular velocity;
- transducer means for recovering a recorded signal from said record;
- signal processing means responsive to a first component of the recovered signal for producing a timebase error correction signal;
- feedback means for applying said timebase error correction signal to said transducer means in a sense to minimize timebase errors of said recovered signal thereby forming a closed loop servo system, said system tending to exhibit a loop gain dependent upon the radial position of said transducer with respect to said record;
- loop gain compensating means responsive to a second component of said recovered signal for regulating the loop gain of said closed loop servo system, said second component of said recovered video signal comprising a digital signal manifestation representative of the radial position of said transducer means with respect to said video disc record, said loop gain compensating means comprising:
- variable gain amplifier means interposed in said closed loop servo system for regulating said loop gain in accordance with a control signal;
- and
- signal processing means for deriving said control signal from said digital signal manifestation and supplying said control signal to said amplifier means.
5 more elements
A video disc player, comprising:
- turntable means for rotating a video disc record at a predetermined substantially constant angular velocity;
- transducer means for recovering a recorded signal from said record;
- signal processing means responsive to a first component of the recovered signal for producing a timebase error correction signal;
- feedback means applying said timebase error correction signal to said transducer means in a sense to minimize timebase errors of said recovered signal thereby forming a closed loop servo system, said system tending to exhibit a loop gain dependent upon the radial position of said transducer with respect to said record;
- loop gain compensating means responsive to a second component of said recovered signal for regulating the loop gain of said closed loop servo system, said second component of said recovered video signal comprising a digital signal manifestation representative of field indentification numbers of said recovered signal, said loop gain compensating means comprising:
- variable gain amplifier means interposed in said closed loop servo system for regulating said loop gain in accordance with a control signal;
- and
- signal processing means for deriving said control signal from said field identification numbers of said digital signal manifestation.
5 more elements
A video disc player, comprising:
- turntable means for rotating a video disc record at a predetermined substantially constant angular velocity;
- transducer means for recovering a recorded signal from said record;
- signal processing means responsive to a first component of the recovered signal for producing a timebase error correction signal;
- feedback means for applying said timebase error correction signal to said transducer means in a sense to minimize timebase errors of said recovered signal thereby forming a closed loop servo system, said system tending to exhibit a loop gain dependent upon the radial position of said transducer with respect to said record;
- loop gain compensating means responsive to a second component of said recovered signal for regulating the loop gain of said closed loop servo system, said second component of said recovered signal comprising a digital signal manifestation representative of field identification numbers of said recovered signal, said loop gain compensating means comprising:
- variable gain amplifier means interposed in said closed loop servo system for regulating said loop gain in accordance with a digital control signal;
- signal processing means responsive to said digital signal manifestation for dividing said field identification numbers by a given constant to produce a digital playing time indication signal;
- and
- means for applying a component of said digital playing time identification signal as said digital control signal to said amplifier means.
6 more elements
A video disc player comprising:
- turntable means for rotating a video disc record at a predetermined substantially constant angular velocity;
- pickup transducer means for recovering a recorded video signal from said record, the recovered video signal including a color burst component and a pulse code modulated data component;
- timebase error correction servo system means responsive to timebase errors of said color burst component for supplying a feedback signal to said transducer means in a sense to minimize timebase errors of said recovered signal, said servo system means tending to exhibit a loop gain dependent upon the radial position of said pick-up transducer with respect to said record;
- variable gain amplifier means interposed in a signal path in said servo system means for controlling the magnitude of said feedback signal in response to a control signal supplied thereto;
- signal processing means responsive to said pulse code modulated data component of said recovered video signal for producing said control signal;
- and
- means for applying said control signal to said amplifier means in a sense to counteract the tendency of the loop gain of said servo system to change with the radial position of said pickup transducer with respect to said record.
4 more elements
Dependencies are inferred from the claim text.