| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical drive device which can perform layer identifying processing even if an interlayer distance is small while avoiding division of a main beam receiving face as much as possible. SOLUTION: The optical drive device includes: a diffraction grating that divides a light beam radiated to a multilayer optical disk having a plurality of recording layers into a main beam and first and second sub-beams; a photodetector 5 that has a main beam receiving face and first and second sub-beam receiving faces, which are arranged so as to be able to receive the main beam and the first and second sub-beams reflected at the multilayer optical disk, and that outputs signals showing the amount of light received for each receiving face; a pull-in signal generating section 61a that generates a pull-in signal based on a total signal of a first output signal of the photodetector 5, which shows the amount of light received of the first sub-beam light receiving face, and a second output signal of the photodetector 5, which shows the amount of light received of the second sub-beam light receiving face; and an objective lens controlling section 65 that performs layer identifying processing based on the pull-in signal. COPYRIGHT: (C)2011,JPO&INPIT
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