Optical pickup, optical disc apparatus, and radial tilt detection method

The invention relates to an optical pickup, optical disc apparatus, and radial tilt detection method. The optical pickup apparatus according to an embodiment of the invention has an object lens (26) which captures a light beam reflected on a recording surface of an optical disc D, a polarization control element (24) which divides a light beam captured by the object lens into a predetermined number of beams, and diffracts each divided beam in a predetermined direction, a photodetector (27) which detects a light beam divided and diffracted by the polarization control element for each divided component, and a signal processor (2) which calculates a tilt component (radial tilt) along the radial direction of am optical disc, in an output of the photodetector, as a difference between a signal component (FES) indicating a change in the distance from the object lens to an optical disc, and a signal component (DPD) indicating a position in the radial direction of a string cf signal components recorded in an optical disc.