Servo control signal generation device and an optical disk device using the same

A servo control signal generation device corresponding to reproduction of optical disks having a reflectance after recording which is lower than that before recording and optical disks having a reflectance after recording which is higher than that before recording, said servo control signal generation device comprising:

• a RF generator which generates a RF signal on the basis of reflected light of an optical disk;
• a top envelope generator which generates a top envelope signal of the RF signal;
• a bottom envelope generator which generates a bottom envelope signal of the RF signal;
• a signal generator which generates, when the optical disk belongs to a kind of optical disks having a reflectance after recording which is lower than that before recording, a defect signal from the top envelope signal and a mirror signal from the bottom envelope signal, and generates, when the optical disk belongs to a kind of optical disks having a reflectance after recording which is higher than that before recording, a defect signal from the bottom envelope signal and a mirror signal from the top envelope signal;
• and
• a polarity changer which changes over polarity of said mirror signal according to whether the optical disk belongs to a kind of optical disks having a reflectance after recording which is lower than that before recording, or the optical disk belongs to a kind of optical disks having a reflectance after recording which is higher than that before recording.

A servo control signal generation device corresponding to reproduction of optical disks having a reflectance after recording which is lower than that before recording and optical disks having a reflectance after recording which is higher than that before recording, said servo control signal generation device comprising:

• a RF generator which generates a RF signal on the basis of reflected light of an optical disk;
• a top envelope generator which generates a top envelope signal of the RF signal;
• a bottom envelope generator which generates a bottom envelope signal of the RF signal;
• a first selector which selects and outputs the top envelope signal when the optical disk belongs to a kind of optical disks having a reflectance after recording which is lower than that before recording, and selects and outputs the bottom envelope signal when the optical disk belongs to a kind of optical disks having a reflectance after recording which is higher than that before recording;
• a second selector which selects and outputs the bottom envelope signal when the optical disk belongs to a kind of optical disks having a reflectance after recording which is lower than that before recording, and selects and outputs the top envelope signal when the optical disk belongs to a kind of optical disks having a reflectance after recording which is higher than that before recording;
• a first detector which detects when an output signal level of said first selector is lower than a first predetermined level;
• a low frequency band rejection unit which removes a DC component from an output signal of said second selector;
• a second detector which detects when an output signal level of said low frequency band rejection unit is higher than a second predetermined level;
• and
• a polarity changer which changes over polarity of an output signal from said second detector according to whether the optical disk belongs to a kind of optical disks having a reflectance after recording which is lower than that before recording, or the optical disk belongs to a kind of optical disks having a reflectance after recording which is higher than that before recording, wherein an output signal of said first detector is used as a defect signal, and an output signal of said polarity changer is used as a mirror signal.

A servo control signal generation device corresponding to reproduction of optical disks having a reflectance after recording which is lower than that before recording and optical disks having a reflectance after recording which is higher than that before recording, said servo control signal generation device comprising:

• a RF generator which generates a RF signal on the basis of reflected light of an optical disk;
• a top envelope generator which generates a top envelope signal of the RF signal;
• a bottom envelope generator which generates a bottom envelope signal of the RF signal;
• a changeover unit which changes over between the top envelope signal and the bottom envelope signal and outputs a resultant signal;
• a low frequency band rejection unit which removes a DC component from the output of said changeover unit;
• a top hold unit which holds a top level of an output of said low frequency band rejection unit;
• a bottom hold unit which holds a bottom level of an output of said low frequency band rejection unit;
• a potentiometer which conducts voltage division between an output signal of said top hold unit and an output signal of said bottom hold unit and outputs a resultant signal;
• a comparator which compares the output of said low frequency band rejection unit with an output of said potentiometer and outputs a two-valued signal obtained by the comparison as a mirror signal;
• and
• a polarity changer which changes over polarity of said mirror signal according to whether the optical disk belongs to a kind of optical disks having a reflectance after recording which is lower than that before recording, or the optical disk belongs to a kind of optical disks having a reflectance after recording which is higher than that before recording, wherein when the optical disk belongs to a kind of optical disks having a reflectance after recording which is lower than that before recording, said changeover unit outputs the bottom envelope signal, and when the optical disk belongs to a kind of optical disks having a reflectance after recording which is higher than that before recording, said changeover unit outputs the top envelope signal.