Write clock generation circuit and optical disk apparatus

A wobble signal generation circuit for generating wobble signal based on a wobbling track formed on a recording medium, comprising:

• two variable gain amps that amplify respective signals from a photo detector divided into two portions by a dividing line corresponding to a tangential direction of the track at a determined gain;
• a gain control circuit that determines the gain of said variable gain amps in a particular period immediately after the beginning of data-writing by varying the gain of said variable gain amps stepwise;
• and
• a subtracter that produces wobble signal by subtracting outputs from said respective variable gain amps.

A made-binary wobble signal generation circuit for generating made-binary wobble signal based on a wobbling track formed on a recording medium, comprising:

• a subtracter that produces wobble signal by subtracting respective signals from a photo detector divided into at least two portions with a dividing line corresponding to a tangential direction of the track;
• a variable gain amp that amplifies the wobble signal output from said subtracter at a determined gain;
• a gain control circuit that determines the gain of said variable gain amps in a particular period immediately after data-writing has been started by varying the gain of said variable gain amps stepwise;
• a wobble amplitude regulation AGC circuit that automatically controls gain thereof so as to regulate amplitude of the wobble signal output from said variable gain amp;
• and
• a making-binary circuit that digitizes signals output from said wobble amplitude regulation AGC circuit into made-binary wobble signal.

A method of generating wobble signal based on a wobbling track formed on a recording medium, the method comprising the steps of:

• capturing a photo signal;
• dividing the captured photo signal into two portions by a dividing line corresponding to a tangential direction of the track;
• amplifying the divided signals at a gain varied stepwise in a particular period immediately after the beginning of data-writing;
• and
• subtracting the amplified signals thereby to produce the wobble signal.

A method of generating write clock from wobble signal based on a wobbling track formed on a recording medium, the method comprising the steps of:

• capturing a photo signal;
• dividing the captured photo signal into two portions by a dividing line corresponding to a tangential direction of the track;
• amplifying the divided signals at a gain varied stepwise in a particular period immediately after the beginning of data-writing;
• subtracting the amplified signals thereby to produce the wobble signal;
• regulating amplitude of the produced wobble signal thereby to obtain amplitude-regulated wobble signal;
• digitizing the obtained amplitude-regulated wobble signal into made-binary wobble signal;
• and
• generating write clock using the made-binary wobble signal as a reference.

A method of generating made-binary wobble signal based on a wobbling track formed on a recording medium, the method comprising the steps of:

• capturing a photo signal;
• dividing the captured photo signal into two portions by a dividing line corresponding to a tangential direction of the track;
• subtracting the divided signals;
• amplifying the subtracted signals at a gain varied stepwise in a particular period immediately after the beginning of data-writing thereby to produce a wobble signal;
• regulating amplitude of the produced wobble signal thereby to obtain amplitude-regulated wobble signal;
• and
• digitizing the obtained amplitude-regulated wobble signal into made-binary wobble signal.

A method of generating write clock from wobble signal based on a wobbling track formed on a recording medium, the method comprising the steps of:

• capturing a photo signal;
• dividing the captured photo signal into two portions by a dividing line corresponding to a tangential direction of the track;
• subtracting the divided signals;
• amplifying the subtracted signals at a gain varied stepwise in a particular period immediately after the beginning of data-writing thereby to produce a wobble signal;
• regulating amplitude of the produced wobble signal thereby to obtain amplitude-regulated wobble signal;
• digitizing the obtained amplitude-regulated wobble signal into made-binary wobble signal;
• and
• generating write clock using the made-binary wobble signal as a reference.