Hitachi, Ltd.

Kouichirou Nishimura

Kouichi Hirose

Toshifumi Takeuchi

Manabu Katsuki

The present invention has an object to stably reproduce wobble signals of all disks of CD-R/RW, DVD-R/RW and DVD-RAM by one wobble signal reproducing circuit. In the wobble signal reproducing circuit, an AGC (AUTOMATIC GAIN CONTROL) circuit for equating a push-pull circuit output of a wide range and an RF amplitude of an optical detector output of two systems obtained by push-pull, and an AGC (AUTOMATIC GAIN CONTROL) circuit for making a wobble amplitude uniform are provided with a function to hold a gain or to change over a response time constant, and at the time of reproduction of the DVD-R/RW, a land pre-pit region is detected by the push-pull output to hold AGC (AUTOMATIC GAIN CONTROL) or change over a response time constant. Besides, in an address information recording region (PID region) at the time of reproduction of the DVD-RAM, the AGC (AUTOMATIC GAIN CONTROL) is held or the response time constant is changed over.

Wobble signal reproducing circuit

An adaptive equalizer processing an input having a fluctuating amplitude realizes a stable adaptive equalization operation without changing over a reference value for computing an equalization error. An input signal is held as a sample with a timing signal shifted from a reference clock of the input signal by a phase ofcycle. An equalization output is compute from sample data. The difference between only the first output value after a zero-crossing and an arbitrary reference value is computed, and the computed value is set as an equalization error. A coefficient of the adaptive equalization circuit is updated from the equalization error and the sample data. To stabilize for displacement of symmetry of the input, the reference value of the equalizer is changed corresponding to the change of a digitization threshold value of a digitization circuit which constitutes a rear stage of the adaptive equalizer.

Adaptive equalizer circuit

The present invention has an object to stably reproduce wobble signals of all disks of CD-R/RW, DVD-R/RW and DVD-RAM by one wobble signal reproducing circuit. In the wobble signal reproducing circuit, an AGC (AUTOMATIC GAIN CONTROL) circuit for equating a push-pull circuit output of a wide range and an RF amplitude of an optical detector output of two systems obtained by push-pull, and an AGC circuit for making a wobble amplitude uniform are provided with a function to hold a gain or to change over a response time constant, and an address information recording region (PID region) at the time of reproduction, the AGC (AUTOMATIC GAIN CONTROL) is held or the response time constant is changed over.

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Ebina, Japan

Kouichirou Nishimura