| 摘要 |
PURPOSE: An optical pickup system is provided to simplify the structure of a beam generating/detecting module and to perform focusing and tracking exactly. CONSTITUTION: LDs(Laser Diode,22a,24a) emit laser beams to an optical disk(40). A first and a second beam generating/detecting modules(22,24) have photodetectors(22b,24b) for detecting the laser beams reflected from the optical disk and generate laser beams having different polarization characteristics. An objective lens(38) focuses the laser beams on the recording face of the optical disk. A DBS(Dichroic Beam Splitter,26) integrates the paths of the laser beams emitted toward the objective. A quarter wave plate(32) changes the polarization characteristics of the laser beams. A selective diffraction grating(34) reduces linear velocity by diffracting a part of the laser beams of the objective lens depending on the polarization characteristics and focuses the laser beam on the photodetectors by diffracting the laser beams of the DBS. Thereby, an optical disk system accesses two kinds of disks by using the DBS and the selective diffraction grating.
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