Patent ID: 7558170

Claim:
An optical information apparatus, comprising: an optical pick-up head including: a light source emitting a light beam; a condensing unit receiving beams from the light source and condensing the beams onto an optical recording medium; a beam splitter receiving the beams reflected from the optical recording medium and splitting the beams; and a photodetector receiving the beams split by the beam splitter in at least four light-receiving portions and outputting signals in accordance with amounts of the received beams; and a tracking error signal generator generating a tracking error signal for irradiating a desired track with a beam, the optical recording medium having tracks at a track pitch of tp, wherein assuming that a signal proportional to a difference between light amounts of two regions divided by a dividing line that passes through a center of the beam and is parallel to the track is a push-pull signal, and an amplitude of the push-pull signal is fluctuated when the light beam is scanned in a direction orthogonal to the track of the optical recording medium, the tracking error signal generator obtains a tracking error signal by an arithmetic operation: (I 1 −I 2 )−k(I 3 −I 4 ), where assuming that outputs of the four light-receiving portions receiving the beam are I 1 to I 4 , and k is a real number, signals I 1 and I 2 output from the light-receiving portions are signals output from the light-receiving portions which have received a region where 0 th order diffracted light that is simply reflected from the optical recording medium and 1 st order diffracted light that is diffracted by tracks at the track pitch of to of the optical recording medium are overlapped with each other, and signals I 3 and I 4 output from the light-receiving portions are signals output from the light-receiving portions which have received most of a region where the 0 th order diffracted light that is simply reflected from the optical recording medium and the 1st order diffracted light that is diffracted by the tracks at the track pitch of tp of the optical recording medium are not overlapped with each other.