Photodetector unit, and optical pickup, optical reproduction apparatus, and optical recording apparatus equipped with the same

Abstract

An optical pickup that is equipped with a photodetector unit, irradiates an optical disc with a laser beam, and receives returning light reflected by the optical disc, where the optical pickup is constructed to (1) divide the laser beam into a main beam, a preceding sub-beam, and a succeeding sub-beam, (2) direct the main beam, the preceding sub-beam, and the succeeding sub-beam toward the optical disc, and (3) divide returning lights of the main beam, the preceding sub-beam, and the succeeding sub-beam respectively into first-fourth main returning lights, first-fourth preceding returning lights, and first-fourth succeeding returning lights, and the photodetector unit includes: first-fourth main photodetectors that respectively receive the first-fourth main returning lights; first-fourth preceding photodetectors that respectively receive the first-fourth preceding returning lights; and first-fourth succeeding photodetectors that respectively receive the first-fourth succeeding returning lights. A tracking error signal appropriate to the optical disc to be reproduced is selected from three tracking error signals detected according to the detection signals from the photodetectors, and a tracking servo is driven according to the selected tracking error signal.