| 摘要 |
An optical head apparatus for a phase change disk includes a semiconductor laser, a rectangular prism, diffraction gratings, an optical sensor element, and a four-divisional optical sensor. The semiconductor laser outputs a laser beam. The rectangular prism has an inclined surface formed with a polarizing beam splitter film, and deflects the laser beam emitted from the semiconductor laser by 90 DEG toward an optical disk. The polarizing beam splitter passes a return beam of the laser beam which is reflected by the optical disk. The diffraction gratings are arranged in contact with or close to the inclined surface of the prism, and generate a 0th-order polarized laser beam and +/-1st-order polarized laser beams from the beam returning from the optical disk through the rectangular prism. The optical sensor element detects the 0th-order polarized laser beam output from the diffraction gratings. A reproducing signal is obtained from an output from the optical sensor element. The four-divisional optical sensor detects one of the +/-1st-order polarized laser beams output from the diffraction gratings. A focusing error signal and a tracking error signal are obtained based on an output from the four-divisional optical sensor.
|
