| 摘要 |
According to one embodiment, an optical pick up apparatus according to an embodiment of the invention has an object lens which captures a light beam reflected on a recording surface of an optical disc, a polarization control element 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 which detects a light beam divided and diffracted by the polarization control element for each divided component, and a signal processor which calculates a tilt component along the radial direction of am optical disc, in an output of the photodetector, as a difference between a signal component indicating a change in the distance from the object lens to an optical disc, and a signal component indicating a position in the radial direction of a string of signal components recorded in an optical disc.
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