Video disc transmission line and stylus RF return systems

Claim 2

An information playback system for recovering information recorded on a record medium, said information playback system comprising: pickup means for establishing a reactance subject to variations in accordance with said recorded information; a conductive support housing; an elongated conductive member having first and second ends and being enclosed within said conductive support housing throughout at least a major portion of its length, said first end being pivotally mounted within said support housing so as to permit relative motion between said conductive member and said enclosing support housing, and said second end being mechanically and electrically coupled to said pickup means so that said conductive member mechanically supports said pickup means in a manner permitting motion of said pickup means relative to said housing, and so that a transmission line formed due to the electrical relationship between said conductive member and said enclosing support housing is electrically connected to said pickup means in a manner establishing a tuned circuit which includes the reactance exhibited by said transmission line and the reactance established by said pickup means.

Claim 3

A information playback system as described in claim 1 wherein said pickup means forms a capacitance with said record medium, said capacitance varying as said record is moved.

Claim 4

An information playback system as described in claim 2 including a source of signal energy coupled to said tuned circuit for energizing said tuned circuit such that signals modulated by said record information are developed in said tuned circuit as said record is moved, said playback system also including detector means coupled to said tuned circuit for detecting said modulated signals developed in said tuned circuit.

Claim 5

A information playback system for use with a record medium having information recorded thereon, said system comprising: means for moving said record medium; pickup means for establishing a reactance subject to variations in accordance with the information recorded on said record medium as said medium is moved; said reactance variations comprising capacitive variations between said record medium and said pickup means; a conductive support housing; an elongated conductive member having first and second ends and being enclosed within said conductive support housing throughout at least a major portion of its length, said first end being pivotally mounted within said support housing so as to permit relative motion between said conductive member and said enclosing support housing, and said second end being mechanically and electrically coupled to said pickup means so that said conductive member mechanically supports said pickup means in a manner permitting motion of said pickup means relative to said housing, and so that a transmission line formed due to the electrical relationship between said conductive member and said enclosing support housing is electrically connected to said pickup means in a manner establishing a tuned circuit which includes the reactance exhibited by said transmission line and the reactance established by said pickup means, said tuned circuit having a resonant frequency which is subject to variation over a given range of frequencies as the reactance established by pickup means varies during movement of said record medium; a source of oscillations at a frequency in the immediate vicinity of, but outside, said given range of frequencies; and means, mounted within said conductive support housing, for providing an inductive coupling between said source and said tuned circuit so as to energize said tuned circuit with said oscillations.

Claim 6

A information playback system for use with a record medium having information recorded thereon, said system comprising: means for moving said record medium; pickup means for establishing a reactance subject to variations in accordance with the information recorded on said record medium as said medium is moved; said reactance variations comprising capacitive variations between said record medium and said pickup means; a conductive support housing; an elongated conductive member having first and second ends and being enclosed within said conductive support housing throughout at least a major portion of its length, said first end being pivotally mounted within said support housing so as to permit relative motion between said conductive member and said enclosing support housing, and said second end being mechanically and electrically coupled to said pickup means so that said conductive member mechanically supports said pickup means in a manner permitting motion of said pickup means relative to said housing, and so that a transmission line formed due to the electrical relationship between said conductive member and said enclosing support housing is electrically connected to said pickup means in a manner establishing a tuned circuit which includes the reactance exhibited by said transmission line and the reactance established by said pickup means, said tuned circuit having a resonant frequency which is subject to variation over a given range of frequencies as the reactance established by pickup means varies during movement of said record medium; a source of oscillations at a frequency in the immediate vicinity of, but outside, said given range of frequencies; and means, mounted within said conductive support housing, for providing an inductive coupling between said source and said tuned circuit so as to energize said tuned circuit with said oscillations.

Claim 7

An information playback system as described in claim 4 wherein the length of said conductive member is chosen so that the effective length of said transmission line closely approximates one-quarter wave length at a frequency within said given range of frequencies.

Claim 8

An information playback system as defined in claim 4 including means, mounted within said conductive housing and inductively coupled to said tuned circuit, for detecting variations in the amplitude of oscillations appearing across said tuned circuit.

Claim 9

An information playback system as defined in claim 6 for use with a record medium in the form of a grooved disc record having video information recorded in a groove thereof, wherein said pickup means comprises a groove tracking stylus including a conductive electrode, and wherein the frequency of oscillations provided by said source greatly exceeds the recorded video information frequencies.

Claim 10

An information playback system for use with a disc record having a spiral groove in a surface layer of dielectric material, with video information recorded in said groove, and with a layer of conductive material underlying said surface layer; said system comprising: a source of oscillations at a predetermined frequency; means for rotating said disc record; a conductive housing; a tracking stylus for engaging said record groove during playback of said disc record, said stylus including a conductive electrode for forming a capacitance with said disc record layer of conductive material, said capacitance varying, according to the information recorded in said disc record groove, as said disc record is rotated; an elongated conductive member having first and second ends and being enclosed within said conductive support housing throughout at least a major portion of its length; said first end being pivotally mounted within said support housing so as to permit relative motion between said conductive member and said enclosing support housing; and said second end being mechanically and electrically coupled to said tracking stylus so that said conductive member mechanically supports said tracking stylus in a manner permitting motion of said tracking stylus relative to said housing, and so that a transmission line formed due to the electrical relationship between said conductive member and said enclosing support housing is electrically connected to said stylus electrode in a manner establishing a tuned circuit which includes the reactance exhibited by said transmission line and the varying capacitance formed by said tracking stylus electrode and said disc record layer of conductive material; said tuned circuit having a resonant frequency subject to variation, over a range of frequencies in the immediate vicinity of said predetermined frequency, in response to said capacitance variations; means, mounted within said conductive housing and inductively coupled to said tuned circuit, for applying oscillations from said source to said tuned circuit; and detector means, mounted within said conductive housing and inductively coupled to said tuned circuit, for detecting variations in the response of said tuned circuit to said oscillations, said detector means providing output signals corresponding to said recorded video information.

Claim 11

An information playback system for use with a disc record having a spiral groove in a surface layer of dielectric material, with video information recorded in said groove, and with a layer of conductive material underlying said surface layer; said system comprising: a source of oscillations at a predetermined frequency; means for rotating said disc record; a conductive housing; a tracking stylus for engaging said record groove during playback of said disc record, said stylus including a conductive electrode for forming a capacitance with said disc record layer of conductive material, said capacitance varying, according to the information recorded in said disc record groove, as said disc record is rotated; an elongated conductive member having first and second ends and being enclosed within said conductive support housing throughout at least a major portion of its length; said first end being pivotally mounted within said support housing so as to permit relative motion between said conductive member and said enclosing support housing; and said second end being mechanically and electrically coupled to said tracking stylus so that said conductive member mechanically supports said tracking stylus in a manner permitting motion of said tracking stylus relative to said housing, and so that a transmission line formed due to the electrical relationship between said conductive member and said enclosing support housing is electrically connected to said stylus electrode in a manner establishing a tuned circuit which includes the reactance exhibited by said transmission line and the varying capacitance formed by said tracking stylus electrode and said disc record layer of conductive material; said tuned circuit having a resonant frequency subject to variation, over a range of frequencies in the immediate vicinity of said predetermined frequency, in response to said capacitance variations; means, mounted within said conductive housing and inductively coupled to said tuned circuit, for applying oscillations from said source to said tuned circuit; and detector means, mounted within said conductive housing and inductively coupled to said tuned circuit, for detecting variations in the response of said tuned circuit to said oscillations, said detector means providing output signals corresponding to said recorded video information.

Claim 12

An information playback system as described in claim 8 wherein saId variations of the resonant frequency of said tuned circuit, occurring in response to said capacitive variations between said record layer and said tracking stylus electrode as said record is rotated, cause amplitude modulation of said oscillations applied to said tuned circuit; and wherein said detector means comprises an amplitude modulation detector.

Claim 13

An information playback system for use with a video disc record of a type having a spiral groove in a surface thereof, with the groove bottom geometry varying along said groove in representation of recorded video information, with a conductive layer overlying said grooved surface, and with a dielectric coating overlying said conductive layer; said system comprising: means for rotating said disc record; a stylus for engaging the coated bottom of said record groove during playback of said record, said stylus including a conductive electrode for forming a capacitance with said disc record''s conductive layer, said capacitance being subject to variations in accordance with said groove bottom geometry variations representative of the information recorded on said record as said disc record is rotated; a hollow support housing of conductive material, having a bottom surface with an aperture therein; said housing being subject to orientation during record playback such that said aperture overlies the record groove convolution undergoing stylus engagement under conditions of close spacing between said bottom housing surface and the coated record surface; a stylus support arm of conductive material extending within said conductive support housing between a first end, pivotally mounted within said housing to permit pivotal motion of said arm relative to said housing, and a second end, located in the vicinity of said aperture and subject to protrusion therethrough during record playback; said conductive support housing bottom surface being shaped and dimensioned relative to the periphery of said aperture such that the area of said bottom surface overshadowing the coated record surface during stylus engagement of the outermost record groove convolution forms a capacitance with the record''s conductive layer that is many times greater than the capacitance formed between said conductive electrode of said stylus and the record''s conductive layer; means for mechanically and electrically coupling said stylus to said second end of said stylus support arm such that (a) said stylus is mechanically supported by said second end of said support arm and (b) said stylus electrode is electrically connected to said second end of said conductive support arm.

Claim 14

An information playback system for use with a video disc record of a type having a spiral groove in a surface thereof, with the groove bottom geometry varying along said groove in representation of recorded video information, with a conductive layer overlying said grooved surface, and with a dielectric coating overlying said conductive layer; said system comprising: means for rotating said disc record; a stylus for engaging the coated bottom of said record groove during playback of said record, said stylus including a conductive electrode for forming a capacitance with said disc record''s conductive layer, said capacitance being subject to variations in accordance with said groove bottom geometry variations representative of the information recorded on said record as said disc record is rotated; a hollow support housing of conductive material, having a bottom surface with an aperture therein; said housing being subject to orientation during record playback such that said aperture overlies the record groove convolution undergoing stylus engagement under conditions of close spacing between said bottom housing surface and the coated record surface; a stylus support arm of conductive material extending within said conductive support housing between a first end, pivotally mounted within said housing to permit pivotal motion of said arm relative to said housing, and a second end, located in the vicinity of said aperture and subject to protrusion therethrough during record playback; said conductive support housing bottom surface being shaped and dimensioned relative to the periphery of said aperture such that the area of said bottom surface overshadowing the coated record surface during stylus engagement of the outermost record groove convolution forms a capacitance with the record''s conductive layer that is many times greater than the capacitance formed between said conductive electrode of said stylus and the record''s conductive layer; means for mechanically and electrically coupling said stylus to said second end of said stylus support arm such that (a) said stylus is mechanically supported by said second end of said support arm and (b) said stylus electrode is electrically connected to said second end of said conductive support arm.

Claim 15

An information playback system as described in claim 10 wherein said capacitance between housing surface and record layer is approximately two orders of magnitude greater than the value of said capacitance formed between stylus electrode and record layer.

Claim 16

An information playback system as described in claim 11 wherein said greater capacitance has a value of at least approximately 10 pf.

Claim 17

An information playback system in accordance with claim 10 wherein a tuned circuit which includes (1) the reactance exhibited by a transmission line formed by said conductive stylus support arm and the enclosing conductive housing, and (2) the capacitance formed by said stylus electrode and said conductive record layer, is completed during record playback by (3) the capacitance formed by the overshadowing area of said housing bottom surface and said conductive record layer, said tuned circuit having a resonant frequency which is subject to variation over a range of frequencies in response to said stylus-record capacitance variations as said record is rotated; and wherein said system also includes: a source of oscillations at a predetermined frequency in the immediate vicinity of said range of frequencies; means, mounted within said conductive housing and inductively coupled to said tuned circuit, for applying osCillations from said source to said tuned circuit; and detector means, mounted within said conductive housing and inductively coupled to said tuned circuit, for detecting variations in the response of said tuned circuit to said oscillations.