Optical pick-up head apparatus with optical means having polarization anisotropy

An optical pick-up head apparatus comprising:

• a laser source for emitting a going beam;
• an imaging optics for receiving said going beam emitted from said laser source and focusing this beam onto a tiny spot of a magneto-optical recording medium;
• first optical means for splitting a returning beam diffracted at the magneto-optical recording medium and reflected back through said imaging optics into first and second returning beams, said first optical means having polarization anisotropy;
• second optical means for receiving said first returning beam split by the first optical means and further splitting said first returning beam into a plurality of first detecting beams of different directions in accordance with polarization direction of the first returning beam;
• a first photodetector unit having a plurality of photodetectors for receiving said plurality of first detecting beams split by the second optical means and generating photoelectric currents in response to respective first detecting beams;
• third optical means for receiving said second returning beam split by the first optical means and further splitting this beam, said third optical means having polarization anisotropy;
• a focusing-error detecting element for receiving said beam split by the third optical means and generating a second detecting beam for obtaining a focusing-error signal;
• a second photodetector unit having a plurality of photodetectors for receiving said second detecting beam generated from said focusing-error detecting element and respectively generating photoelectric current in response to said second detecting beam;
• and
• a polarization rotator element, disposed on an optical path between said first optical means and said third optical means to rotate polarization direction of the going beam emitted from the laser source and also rotate polarization direction of the returning beam reflected back at the magneto-optical recording medium, thereby differentiating the polarization directions of said going and returning beams;
• wherein said going beam emitted from said laser source advances to said magneto-optical recording medium via a going optical path passing through said third optical means, said polarization rotator element, said first optical means, and said imaging optics, and the returning beam reflected at the magneto-optical recording medium returns to said second photodetector unit via a returning optical path passing through said imaging optics, said first optical means, said polarization rotator element, said third optical means, and said focusing error detecting element.