Focus search method and controller for digital disk

A focus search method for a digital disk, comprising the steps of:

• first focusing an emitted light beam at an initial position at an outer side of either of two recording layers of a digital disk in which a plurality of recording layers are formed;
• moving the focus close to a recording layer side;
• receiving a reflected light beam from the digital disk;
• carrying out control to focus the received light beam on a specified layer;
• and
• performing a layer jump in response to an instruction indicating a layer change;
• wherein, if an improper layer jump has taken place, focusing control is carried out from the same side only for a layer jump to a layer on the initial position side at the time of immediately preceding focusing control.

A focus search method for a digital disk, comprising the steps of:

• bringing a focus of an emitted light beam close to a recording layer from an outer side of any of the recording layers of a digital disk in which a plurality of recording layers are formed;
• receiving a reflected light beam from the digital disk;
• carrying out control to focus the received light beam on a specified layer;
• and
• performing a layer jump in response to an instruction indicating a layer change;
• wherein, if a layer jump has been performed improperly, then an exclusive logical OR of a flag corresponding to a focusing direction and a flag corresponding to a layer specified for a jump is computed to set a next focusing direction.

A focus search method for a digital disk, comprising the steps of:

• first focusing an emitted light beam at an initial position at an outer side of either of two recording layers of a digital disk in which a plurality of recording layers are formed;
• moving the focus close to a recording layer side to receive a reflected light beam from the digital disk;
• carrying out control to focus the received light beam on a specified layer;
• and
• performing a layer jump in response to an instruction indicating a layer change;
• wherein, if a layer jump has been performed improperly, then an exclusive logical OR of a flag corresponding to an initial focus position and a flag corresponding to a layer specified for a jump is computed to set a next initial focus position.

A focus search controller for a digital disk, comprising:

• focusing control means for moving a focus of an emitted light beam close to a recording layer side from an outer side of either of two recording layers of a digital disk in which at least two recording layers, namely, a first layer and a second layer, are formed and for receiving a reflected light beam from the digital disk to carry out control to focus the received light beam on a specified layer;
• and
• layer jump means for performing a layer jump in response to an instruction indicating a layer change;
• the controller further comprising layer jump control means for carrying out focusing control from the same direction only if a layer jump to the second layer has been improperly performed when an immediately preceding focus search was started from an outer side of the second layer, or only if a layer jump to the first layer has been improperly performed when an immediately preceding focus search was started from an outer side of the first layer.

A focus search controller for a digital disk, comprising:

• focusing control means for focusing an emitted light beam first at an initial position on an outer side of either of two recording layers of a digital disk in which a plurality of recording layers are formed, and moving the focus close to a recording layer side so as to receive a reflected light beam from the digital disk and to carry out control to focus the received light beam on a specified layer;
• and
• layer jump means for performing a layer jump in response to an instruction indicating a layer change;
• the controller further comprising layer jump control means for carrying out focusing control from the same side only for a layer jump to a layer on the initial position side during immediately preceding focusing control if an improper layer jump has taken place.

A focus search controller for a digital disk, comprising:

• focusing control means for bringing a focus of an emitted light beam close to a recording layer from an outer side of any of the recording layers of a digital disk, in which a plurality of recording layers are formed, for receiving a reflected light beam from the digital disk, and for carrying out control to focus the received light beam on a specified layer;
• and
• layer jump means for performing a layer jump in response to an instruction indicating a layer change;
• the controller further comprising focus direction setting means for computing an exclusive logical OR of a flag corresponding to a focusing direction and a flag corresponding to a layer specified for a jump to set a next focusing direction if a layer jump has been performed improperly.

A focus search controller for a digital disk, comprising:

• focusing control means for focusing an emitted light beam first at an initial position on an outer side of either of two recording layers of a digital disk, in which a plurality of recording layers are formed, for moving the focus close to a recording layer side so as to receive a reflected light beam from the digital disk, and for carrying out control to focus the received light beam on a specified layer;
• and
• layer jump means for performing a layer jump in response to an instruction indicating a layer change;
• the controller further comprising:
• means for setting a first flag corresponding to an initial position of the focus;
• means for setting a second flag corresponding to a layer specified for a jump;
• arithmetic means for computing an exclusive logical OR of the two flags;
• and
• initial focus position setting means for setting a next initial focus position on the basis of the computation result.