Videodisc focusing and tracking servo

Claim 1

An apparatus for recording and/or reading information tracks in a recording surface of a disk with a beam of radiation, said apparatus comprising means for supporting the disk for rotation in a plane which is parallel to the plane of said recording surface, a frame, an objective having an optical axis and a lens system for converging the radiation beam to a radiation spot, means for supporting said objective in said frame for movement from a neutral position at which said optical axis is at a predetermined position which is perpendicular to said plane of rotation of the disk along a curved path towards and away from said plane of rotation such that during said movement of said objective along said curved path said optical axis continuously tilts with respect to said predetermined position thereof so as to correct for obliqueness of said recording surface of the disk and means for moving said objective so as to focus said spot on the recording surface, said supporting means including a bearing arrangement for supporting said objective in said frame, said bearing arrangement comprising a pivotal device which connects said objective to said frame, said pivotal device, said objective and said frame together forming a qudrangular linkage, said objective and said frame forming opposite sides of said quadrangular linkage and the other two sides of said linkage being formed by said pivotal device, and wherein said two other sides form an acute angle with each other.

Claim 2

An apparatus for recording and/or reading information tracks in a recording surface of a disk with a beam of radiation, said apparatus comprising means for supporting the disk for rotation in a plane which is parallel to the plane of said recording surface, a frame, an objective having an optical axis and a lens system for converging the radiation beam to a radiation spot, means for supporting said objective in said frame for movement from a neutral position at which said optical axis is at a predetermined position which is perpendicular to said plane of rotation of the disk along a curved path towards and away from said plane of rotation such that during said movement of said objective along said curved path said optical axis continuously tilts with respect to said predetermined position thereof so as to correct for obliqueness of said recording surface of the disk and means for moving said objective so as to focus said spot on the recording surface, said supporting means including a bearing arrangement for supporting said objective in said frame, said bearing arrangement comprising a pivotal device which connects said objective to said frame, said pivotal device, said objective and said frame together forming a qudrangular linkage, said objective and said frame forming opposite sides of said quadrangular linkage and the other two sides of said linkage being formed by said pivotal device, and wherein said two other sides form an acute angle with each other.

Claim 4

An apparatus for recording and/or reading information tracks in a recording surface of a disk with a beam of radiation, said apparatus comprising means for supporting the disk for rotation in a plane which is parallel to the plane of said recording surface, a frame, an objective having an optical axis and a lens system for converging the radiation beam to a radiation spot, means for supporting said objective in said frame for movement from a neutral position at which said optical axis is at a predetermined position which is perpendicular to said plane of rotation of the disk along a curved path towards and away from said plane of rotation such that during said movement of said objective along said curved path said optical axis continuously tilts with respect to said predetermined position thereof so as to correct for obliqueness of said recording surface of the disk and means for moving said objective so as to focus said spot on the recording surface, said supporting means including mechanical guide means for guiding said objective along said curved path, said guide means comprising a first and second bearing arrangement which guide said objective at locations which are spaced from each other in a direction parallel to said optical axis of said objective so as to guide said objective in a first and second direction, respectively, which directions make an angle with each other.

Claim 5

An apparatus for recording and/or reading information tracks in a recording surface of a disk with a beam of radiation, said apparatus comprising means for supporting the disk for rotation in a plane which is parallel to the plane of said recording surface, a frame, an objective having an optical axis and a lens system for converging the radiation beam to a radiation spot, means for supporting said objective in said frame for movement from a neutral position at which said optical axis is at a predetermined position which is perpendicular to said plane of rotation of the disk along a curved path towards and away from said plane of rotation such that during said movement of said objective along said curved path said optical axis continuously tilts with respect to said predetermined position thereof so as to correct for obliqueness of said recording surface of the disk and means for moving said objective so as to focus said spot on the recording surface, said supporting means including mechanical guide means for guiding said objective along said curved path, said guide means comprising a first and second bearing arrangement which guide said objective at locations which are spaced from each other in a direction parallel to said optical axis of said objective so as to guide said objective in a first and second direction, respectively, which directions make an angle with each other.

Claim 7

An apparatus for recording and/or reading information tracks in a recording surface of a disk with a beam of radiation, said apparatus comprising means for supporting the disk for rotation in a plane which is parallel to the plane of said recording surface, a frame, an objective having an optical axis and a lens system for converging the beam of radiation to a radiation spot, means for supporting said objective in said frame in a position such that said optical axis is generally perpendicular to said plane of rotation, said objective being supported by said supporting means for axial movement in a direction parallel to said optical axis so as to enable focusing of said spot on said recording surface and for pivotal movement about a pivotal axis which is generally perpendicular to said optical axis, means for detecting focusing errors, means responsive to said focus error detection means for moving said objective in said axial direction so as to correct focusing errors, means for tilting said objective about said pivotal axis, a tracking detector which supplies an electrical tracking signal, an angle detector which supplies an angle error signal representative of the angle between said optical axis and the normal to said recording surface at a location where said optical axis intersects said recording surface, means for adding said tracking and angle error signals, said adding means supplying a further signal representative of the sum of said tracking and angle error signals, and wherein said tilting means is responsive to said further signal.

Claim 8

An apparatus for recording and/or reading information tracks in a recording surface of a disk with a beam of radiation, said apparatus comprising means for supporting the disk for rotation in a plane which is parallel to the plane of said recording surface, a frame, an objective having an optical axis and a lens system for converging the beam of radiation to a radiation spot, means for supporting said objective in said frame in a position such that said optical axis is generally perpendicular to said plane of rotation, said objective being supported by said supporting means for axial movement in a direction parallel to said optical axis so as to enable focusing of said spot on said recording surface and for pivotal movement about a pivotal axis which is generally perpendicular to said optical axis, means for detecting focusing errors, means responsive to said focus error detection means for moving said objective in said axial direction so as to correct focusing errors, means for tilting said objective about said pivotal axis, a tracking detector which supplies an electrical tracking signal, an angle detector which supplies an angle error signal representative of the angle between said optical axis and the normal to said recording surface at a location where said optical axis intersects said recording surface, means for adding said tracking and angle error signals, said adding means supplying a further signal representative of the sum of said tracking and angle error signals, and wherein said tilting means is responsive to said further signal.

Claim 9

An apparatus for recording and/or reading an information track on a recording surface of a disk with a beam of radiation, said apparatus comprising first means for supporting the disk for rotation in a plane which is parallel to the plane of said recording surface, means for converging the radiation beam along an optical axis into a radiation spot on said recording surface, second means for supporting said beam converging means for movement in a first direction towards and away from said plane of rotation and in a second direction so as to produce movement of the beam transverse to the direction of the track, a focus detector, first control means responsive to said focus detector for controlling the movement of said beam converging means in said first direction so as to maintain said beam focused on said recording surface, a tracking detector and second control means responsive to said tracking detector for controlling the movement of said beam converging means in said second direction so that said radiation spot moves along the track in which the information is recorded or from which the information is read, said second supporting means including mechanical means for guiding the movement of said beam converging means during movement thereof towards or away from said disk in response to said focusing detector, said mechanical guide means guiding the movement of said beam converging means independently of said tracking detector and said second control means along a predetermined path such that the angle between said optical axis and the plane of said recording surface changes in dependence on the amount of displacement of said beam converging means towards or away from the disk so as to correct for obliqueness of said recording surface with respect to said plane of rotation.

Claim 10

An apparatus for recording and/or reading an information track on a recording surface of a disk with a beam of radiation, said apparatus comprising first means for supporting the disk for rotation in a plane which is parallel to the plane of said recording surface, means for converging the radiation beam along an optical axis into a radiation spot on said recording surface, second means for supporting said beam converging means for movement in a first direction towards and away from said plane of rotation and in a second direction so as to produce movement of the beam transverse to the direction of the track, a focus detector, first control means responsive to said focus detector for controlling the movement of said beam converging means in said first direction so as to maintain said beam focused on said recording surface, a tracking detector and second control means responsive to said tracking detector for controlling the movement of said beam converging means in said second direction so that said radiation spot moves along the track in which the information is recorded or from which the information is read, said second supporting means including mechanical means for guiding the movement of said beam converging means during movement thereof towards or away from said disk in response to said focusing detector, said mechanical guide means guiding the movement of said beam converging means independently of said tracking detector and said second control means along a predetermined path such that the angle between said optical axis and the plane of said recording surface changes in dependence on the amount of displacement of said beam converging means towards or away from the disk so as to correct for obliqueness of said recording surface with respect to said plane of rotation.