# US 6,298,020 B1 · Focus search method and controller for digital disk > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 6,298,020 B1 - Document ID: US6298020B1 - Status: Granted - Kind: B1 - Application number: 09/478,771 - Filed: 2000-01-06 - Granted: 2001-10-02 - Earliest claimed: 1999-01-21 - Assignees: Alpine Electronics, Inc. - Inventors: Yusuke Kumagami - Web page: https://patentgrep.com/patent/US6298020B1 ## CPC - G11B 7/08511: {with focus pull-in only} - G11B 7/0948: {specially adapted for detection and avoidance or compensation of imperfections on the carrier, e.g. dust, scratches, dropouts (G11B7/095 takes precedence)} - G11B 2007/0013: {for carriers having multiple discrete layers} - G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R) ## Abstract A focus search method and a controller for a digital disk overcomes a shortcoming of a conventional focus search method in which a focus search on a specified layer is always performed from the same direction if a layer jump for changing a layer has been improperly performed during reproduction from a digital disk such as a DVD having a plurality of recording layers, thus taking much time for the focus search when the focus search is begun from a point away from a specified layer. A focus direction used for an immediately preceding focus search performed from an initial focus search position at the outer side of two recording layers is stored in a focus direction memory of a focus direction setter. Based on the data stored in the memory and a signal indicating the position of a specified layer received from a layer specifier that instructs a layer jump, a setter for handling an improper focus jump makes settings so that a focus search is started from a side closer to the specified layer by performing a logical operation and a flow processing. ## Claims ### Claim 1 A focus search method for a digital disk, comprising the steps of: moving a focus of an emitted light beam close to a recording layer 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; 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 focusing control is carried out from the same direction 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, or 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. ### Claim 2 (depends on 1) A focus search method for a digital disk according to claim 1, wherein focusing control is started from an outer side of a recording layer close to a specified layer at the time of starting up the digital disk. ### Claim 3 (depends on 2) A focus search method for a digital disk according to claim 2, wherein, if the digital disk has a single recording layer, focusing control is started from a predetermined side at the time of a startup. ### Claim 4 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. ### Claim 5 (depends on 4) A focus search method for a digital disk according to claim 4, wherein focusing control is started from an outer side of a recording layer close to a specified layer at the time of starting up the digital disk. ### Claim 6 (depends on 5) A focus search method for a digital disk according to claim 5, wherein, if the digital disk has a single recording layer, focusing control is started from a predetermined side at the time of a startup. ### Claim 7 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. ### Claim 8 (depends on 7) A focus search method for a digital disk according to claim 7, wherein focusing control is started from an outer side of a recording layer close to a specified layer at the time of starting up the digital disk. ### Claim 9 (depends on 8) A focus search method for a digital disk according to claim 8, wherein, if the digital disk has a single recording layer, focusing control is started from a predetermined side at the time of a startup. ### Claim 10 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. ### Claim 11 (depends on 10) A focus search method for a digital disk according to claim 10, wherein focusing control is started from an outer side of a recording layer close to a specified layer at the time of starting up the digital disk. ### Claim 12 (depends on 11) A focus search method for a digital disk according to claim 11, wherein, if the digital disk has a single recording layer, focusing control is started from a predetermined side at the time of a startup. ### Claim 13 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. ### Claim 14 (depends on 13) A focus search controller for a digital disk according to claim 13, further comprising means for specifying an initial position at a startup that carries out focusing control from an outer side of a recording layer near a specified layer. ### Claim 15 (depends on 14) A focus search controller for a digital disk according to claim 14, wherein the means for specifying an initial position at a startup carries out focusing control from a predetermined side if the digital disk has a single recording layer. ### Claim 16 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. ### Claim 17 (depends on 16) A focus search controller for a digital disk according to claim 16, further comprising means for specifying an initial position at a startup that carries out focusing control from an outer side of a recording layer near a specified layer. ### Claim 18 (depends on 17) A focus search controller for a digital disk according to claim 17, wherein the means for specifying an initial position at a startup carries out focusing control from a predetermined side if the digital disk has a single recording layer. ### Claim 19 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. ### Claim 20 (depends on 19) A focus search controller for a digital disk according to claim 19, further comprising means for specifying an initial position at a startup that carries out focusing control from an outer side of a recording layer near a specified layer. ### Claim 21 (depends on 20) A focus search controller for a digital disk according to claim 20, wherein the means for specifying an initial position at a startup carries out focusing control from a predetermined side if the digital disk has a single recording layer. ### Claim 22 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. ### Claim 23 (depends on 22) A focus search controller for a digital disk according to claim 22, further comprising means for specifying an initial position at a startup that carries out focusing control from an outer side of a recording layer near a specified layer. ### Claim 24 (depends on 23) A focus search controller for a digital disk according to claim 23, wherein the means for specifying an initial position at a startup carries out focusing control from a predetermined side if the digital disk has a single recording layer.