Control system for the magnetic head of a magneto-optical disc apparatus

Claim 1

a device for inscribing and/or reading a magneto-optical information carried having a reflecting surface, comprising: a frame; a turntable for supporting a magneto-optical information carried placed thereon; means for mounting said turntable to said frame for rotation about an axis of rotation, an optical unit, including means for producing a radiation beam, and objective for concentrating the radiation beam to form at least one radiation spot in focusing plane; and an actuator for moving the objective in a direction parallel to said axis of rotation, a magnetic unit arranged opposite to and spaced from the optical unit, comprising means for generating a magnetic field which extends into said focusing plane, said means for generating including means for defining a reference plane; and a further actuator for moving said means for generating in a direction parallel to said axis of rotation, a measurement and control system for determining, during operation of the device, a distance between said reference plane of the means for generating and said reflecting surface, and for controlling said further actuator in response to determination of said distance, and means for moving said optical unit and said magnetic unit in a plane transverse to said axis of rotation, characterized in that said measurement and control system comprise a detector unit including two optical detectors arranged for cooperation with said reflecting surface, both detectors being secured to the magnetic unit for movement of the entire detector unit with the magnetic unit, and said two detectors together comprising at least one light source, a reference photocell and a measurement photocell.

Claim 2

a device for inscribing and/or reading a magneto-optical information carried having a reflecting surface, comprising: a frame; a turntable for supporting a magneto-optical information carried placed thereon; means for mounting said turntable to said frame for rotation about an axis of rotation, an optical unit, including means for producing a radiation beam, and objective for concentrating the radiation beam to form at least one radiation spot in focusing plane; and an actuator for moving the objective in a direction parallel to said axis of rotation, a magnetic unit arranged opposite to and spaced from the optical unit, comprising means for generating a magnetic field which extends into said focusing plane, said means for generating including means for defining a reference plane; and a further actuator for moving said means for generating in a direction parallel to said axis of rotation, a measurement and control system for determining, during operation of the device, a distance between said reference plane of the means for generating and said reflecting surface, and for controlling said further actuator in response to determination of said distance, and means for moving said optical unit and said magnetic unit in a plane transverse to said axis of rotation, characterized in that said measurement and control system comprise a detector unit including two optical detectors arranged for cooperation with said reflecting surface, both detectors being secured to the magnetic unit for movement of the entire detector unit with the magnetic unit, and said two detectors together comprising at least one light source, a reference photocell and a measurement photocell.

Claim 6

A device for inscribing and/or reading a magneto-optical information carrier having a detectable surface, comprising: a frame; a turntable for supporting a magneto-optical information carried place thereon; and means for mounting said turntable to said frame for rotation about an axis of rotation, an optical unit, including means for producing a radiation beam; an objective for concentrating the radiation beam to form at least one radiation spot in a focusing plane; and an actuator for moving the objective in a direction parallel to said axis of rotation, a magnet unit arranged opposite to and spaced from the optical unit, comprising first means for generating a magnetic field which extends into said focusing plane, said first means for generating including means for defining a reference plane; a supporting element supporting said first means for generating; and a further actuator for moving said supporting element with said first means for generating in a direction parallel to said axis of rotation, a measurement and control system for determining, during operation of the device, a distance between said reference plane of the first means for generating and said detectable surface, and for controlling said further actuator in response to determination of said distance, and means for moving said optical unit and said magnetic unit in a plane transverse to said axis of rotation, characterized in that said measurement and control system comprises: a detector unit entirely arranged on said supporting element for providing an electrical measurement signal responsive to said distance, said detector unit comprising second means for generating a distance measuring signal for cooperation with said detectable surface; means for receiving a measurements signal return from said carrier, said measurement signal being a measure of said distance; and means for providing an electrical measurement signal responsive to said measurement signal, and means, responsive to said electrical measurement signal, for energizing said further actuator.

Claim 7

A device for inscribing and/or reading a magneto-optical information carrier having a detectable surface, comprising: a frame; a turntable for supporting a magneto-optical information carried place thereon; and means for mounting said turntable to said frame for rotation about an axis of rotation, an optical unit, including means for producing a radiation beam; an objective for concentrating the radiation beam to form at least one radiation spot in a focusing plane; and an actuator for moving the objective in a direction parallel to said axis of rotation, a magnet unit arranged opposite to and spaced from the optical unit, comprising first means for generating a magnetic field which extends into said focusing plane, said first means for generating including means for defining a reference plane; a supporting element supporting said first means for generating; and a further actuator for moving said supporting element with said first means for generating in a direction parallel to said axis of rotation, a measurement and control system for determining, during operation of the device, a distance between said reference plane of the first means for generating and said detectable surface, and for controlling said further actuator in response to determination of said distance, and means for moving said optical unit and said magnetic unit in a plane transverse to said axis of rotation, characterized in that said measurement and control system comprises: a detector unit entirely arranged on said supporting element for providing an electrical measurement signal responsive to said distance, said detector unit comprising second means for generating a distance measuring signal for cooperation with said detectable surface; means for receiving a measurements signal return from said carrier, said measurement signal being a measure of said distance; and means for providing an electrical measurement signal responsive to said measurement signal, and means, responsive to said electrical measurement signal, for energizing said further actuator.