Optical disk apparatus having compensation for objective lens dislocation

An optical disc apparatus for applying a light spot to a surface of an optical disc, to record or reproduce information on or from an optical disc, comprising:

• first moving means for moving the light spot radially across the recording surface of an optical disc;
• an optical head comprising converging means for converging the light spot on the surface of an optical disc;
• spot position detection means for generating a spot position signal which indicates a positional difference in a radial direction of an optical disc, between a center of the optical head and the light spot on a receiving element on the optical head;
• first control means for causing a spot position loop filter to filter the spot position signal to generate a first processed signal and outputting the first processed signal to the first moving means;
• second moving means for moving the optical head radially across the surface of an optical disc;
• second control means for causing a traverse loop filter to filter the spot position signal to generate a second processed signal and outputting the second processed signal to the second moving means;
• spot position signal monitoring means for receiving the spot position signal as an input, and outputting a first signal indicating that the spot position signal has a value smaller than a prescribed value;
• and
• system operation control means for operating the first control means when the first signal is input, and operating the second control means after or simultaneously with the operation of the first control means.

An optical disc apparatus for applying a light spot to a surface of an optical disc, to record or reproduce information on or from an optical disc, comprising:

• first moving means for moving the light spot radially across the recording surface of an optical disc;
• an optical head comprising converging means for converging the light spot on the surface of the optical disc;
• spot position detection means for generating a spot position signal which indicates a positional difference in a radial direction of an optical disc, between a center of the optical head and the light spot on a receiving element on the optical head;
• correction signal generation means for receiving the spot position signal as an input, and generating a correction signal for correcting the spot position signal;
• subtracting means for subtracting the correction signal from the spot position signal;
• second moving means for moving the optical head radially across the surface of an optical disc;
• and
• control means for causing a traverse loop filter to filter the spot position signal to generate a second processed signal and outputting the second processed signal to the second moving means.

An optical disc apparatus for applying a light spot to a surface of an optical disc, to record and reproduce information on or from an optical disc, comprising:

• first moving means for moving the light spot radially across the recording surface of an optical disc;
• an optical head comprising converging means for converging the light spot on the surface of an optical disc;
• spot position detection means for generating a spot position signal which indicates a positional difference in a radial direction of the optical disc, between a center of the optical head and the light spot on a receiving element on the optical head;
• second moving means for moving the optical head radially across the surface of an optical disc;
• control means for causing a traverse loop filter to filter the spot position signal to generate a second processed signal and outputting the second processed signal to the second moving means;
• and
• a coefficient multiplier for reducing a control means control coefficient to a value smaller than a normal operation value, at startup of the control means.

An optical disc apparatus for applying a light spot to a surface of an optical disc, to record or reproduce information on or from an optical disc, comprising:

• first moving means for moving the light spot radially across the surface of an optical disc;
• an optical head comprising converging means for converging the light spot on the surface of an optical disc;
• spot position detection means for generating a spot position signal which indicates a positional difference in a radial direction of an optical disc, between a center of the optical head and the light spot on a receiving element on the optical head;
• tracking error detection means for generating a tracking error signal which indicates a positional dislocation between the light spot and a track on an optical disc;
• first control means for causing a spot position loop filter to filter the spot position signal or the tracking error signal to generate a first processed signal and outputting the first processed signal to the first moving means;
• second moving means for moving the optical head radially across the surface of an optical disc;
• control means for causing a traverse loop filter to filter the spot position signal to generate a second processed signal and outputting the second processed signal to the second moving means;
• and
• system operation control means for operating the first control means to cause the phase compensation loop filter to filter the spot position signal, said filtering being a phase-lag compensation and a phase-lead compensation filtering,
• said system operation control means for switching from the spot position signal to the tracking error signal to cause the phase compensation loop filter to filter the tracking error signal, said filtering being a phase-lag compensation and a phase-lead compensation filtering, and operating the second control means after operating the first control means.