Patent ID: 7697393

Claim:
An optical information recording/reproducing apparatus comprising: an optical pickup; and a tracking error signal generation unit which generates a tracking error signal according to a differential push-pull method by executing predetermined operation to signals obtained from the optical pickup; wherein said optical pickup includes: a laser light source which emits a laser light beam; a diffraction grating which diffracts the laser light beam emitted by the laser light source into at least three laser light beams; a beam splitter which transmits the at least three laser light beams; and a detector which detects a reflected light beam from an optical disk, wherein: the diffraction grating includes first, second and third areas, the first area is placed between the second and third areas and the second area has a periodic structure that is shifted from that of the third area by 180° in the phase of the periodic structure, the second and third areas have periodic structures that are phase shifted from that of the first area, the detector includes first, second and third photoreceptor surfaces, and signals from the first, second and third photoreceptor surfaces are combined by addition and/or subtraction.