Patent ID: 7936650

Claim:
An attenuation-amount adjusting circuit comprising: a light irradiating unit that alternately irradiates a laser beam of a writing level and a laser beam of a readout level on an optical disk that has a groove formed by a wobble pattern and plural markers indicating physical positions in the groove; a light receiving unit that receives reflected light of the laser beam irradiated on the optical disk and converts the reflected light into a reproduction signal which includes a writing waveform and a readout waveform; and a writing-waveform attenuating unit that determines a position of a rising edge of the writing waveform corresponding to a beginning of a pit of the groove, the writing waveform corresponding to the reflected light of the laser beam of the writing level in the reproduction signal, the writing-waveform attenuation unit including a plurality of attenuators, a first one of the plurality of attenuators is configured to attenuate an amplitude level of the writing waveform in the reproduction signal at a first level of attenuation, and a second one of the plurality of attenuators is configured to attenuate the amplitude level of the writing waveform in the reproduction signal at a second level of attenuation different from the first level of attenuation according to the determined position of the rising edge of the writing waveform.