Patent ID: 7212486

Claim:
An optical disk device causing a light beam to be projected intermittently with different powers on a disk having a track with a wobbled groove formed along the track undulating in a radial direction of the disk at a predetermined cycle for forming a wobble signal with the track having land areas between grooves on which pre-pits are formed beforehand at locations corresponding to peaks of the wobble along the track in radial directions of the disk, the device comprising: a first detector detecting a portion of a reflected light of said light beam, the portion being reflected from a side of said track at which said pre-pit is formed; a second detector detecting a portion of the reflected light of said light beam, the portion being reflected from the other side of said track; a first amplifier amplifying a first detection signal detected by said first detector with the first detection signal corresponding to a first set of wobble signal components; and a second amplifier amplifying a second detection signal detected by said second detector with the second detection signal corresponding to a second set of wobble signal components, wherein a gain of at least one of said first amplifier and said second amplifier is so set that a peak envelope of the output signal of the first amplifier which corresponds to the peak value of the amplitude of the first set of wobble signal components coincides with a peak envelope of the output signal of the second amplifier which corresponds to the bottom value of amplitude of the second set of wobble signal components for enabling the detection of said pre-pits and for distinguishing the pre-pits from the wobble signal.