Patent ID: 7542382

Claim:
An optical information apparatus, comprising: an optical pick-up head including: a light source emitting a light beam; a condensing unit receiving a beam from the light source and condensing the beam onto an optical recording medium; a beam splitter receiving the beam reflected from the optical recording medium and splitting the beam; and a photodetector receiving the beams split by the beam splitter and outputting signals in accordance with amounts of the received light beams; wherein the photodetector has a plurality of light-receiving portions, and a tracking error signal generator generating a tracking error signal for irradiating a desired track with a beam, wherein the optical recording medium has tracks arranged substantially at a constant pitch, an average of the pitch is tp, the beams are received by the plurality of light-receiving portions, and the tracking error signal generator performs a differential arithmetic operation with respect to the signals output from the light-receiving portions to generate a push-pull signal, and in a case where an amplitude of the push-pull signal, obtained at a pitch tp when the light beam is scanned in a direction orthogonal to the tracks of the optical recording medium, is changed at a pitch different from the pitch tp, the push-pull signal is obtained by an arithmetic operation (I 1 -I 2 )-k(I 3 -I 4 ) where I1 to I4 are the outputs from four light-receiving portions receiving the beams and k is a real number.