Optical pickup and disc drive apparatus

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 smallest 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 Db12, a distance from the centers of the third sub-spots to the centers of the fourth sub-spots is Db34, a distance from the centers of the first sub-spots to the centers of the third sub-spots is Db13, a distance from the centers of the second sub-spots to the centers of the fourth sub-spots is Db24, n12, n34, n13, and n24 are natural numbers, and the track pitch of said arbitrary kind of disc-shaped recording medium is Pb, the distance Db13 is approximately (2n13−1)×Pb/2, the distance Db24 is approximately (2n24−1)×Pb/2, the distance Db12 is approximately (2n12−1)×Pb/4, and the distance Db34 is approximately (2n34−1)×Pb/4, and
• 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.