Patent ID: 7583570
Filing Date: 2009-09-01
Classification: G11B

Abstract:
1. An optical pickup for recording or reproducing information signals on a plurality of kinds of disc-shaped recording media, the optical pickup moving in a radial direction of a disc-shaped recording medium mounted on a disc table while irradiating the disc-shaped recording medium with laser light emitted from a light-emitting element and having a wavelength corresponding to the kind of the disc-shaped recording medium, the optical pickup comprising: a diffracting element having a plurality of regions for dividing the laser light emitted from the light-emitting element into a main beam, a pair of first sub-beams, a pair of second sub-beams, a pair of third sub-beams, and a pair of fourth sub-beams, wherein, when the first, second, third, and fourth sub-beams form first, second, third, and fourth sub-spots, respectively, on a recording surface of a disc-shaped recording medium which does not have the largest track pitch among said plurality of kinds of disc-shaped recording media, said first, second, third, and fourth sub-spots being arranged in that order along a radial direction of said disc-shaped recording medium, and when a distance from the centers of the first sub-spots to the centers of the second sub-spots is Da phases of a plurality of tracking error signals detected by said first, second, third, and fourth sub-spots are inverted from each other and an amplitude of a total tracking error signal obtained by the pairs of sub-beams is zero.