Optical pickup apparatus and focusing control method

摘要

An optical pickup apparatus having an irradiation optical system for condensing a light beam on a track of a recording plane and a photodetection optical system for guiding return light to a photodetector (40) to detect a focal error includes a holographic lens (39) provided in the optical path of the return light for outputting 0-th and +/-1st order diffracted lights based on the return light; an optical element (38) provided in front of or behind the holographic lens for providing astigmatism; photodetectors (400,401,402) for receiving the 0-th and +/-1st order diffracted lights; and servo-signal generating operation circuits connected to the photodetectors (400,401,402) for generating a first and second focus error signals having a first and second capture ranges based on the output signal of the photodetector (40).