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

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.