Optical pickup device and optical disc device

Dynamic information storage or retrieval – Specific detail of information handling portion of system – Radiation beam modification of or by storage medium

Reexamination Certificate

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Reexamination Certificate

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07929399

ABSTRACT:
When recording on and/or reproducing from an information recording medium having a plurality of recording layers is performed, there has been a problem in appropriately detecting a control signal at the time of the recording and/or reproducing, since reflected light from a recording layer, which does not undergo the recording and/or reproducing, enters a photodetector concurrently with reflected light from a recording layer which undergoes the recording and/or reproducing. In the present invention, a polarization hologram is used to diffract light outputted from a light source and to generate a main beam, which is a zeroth-order light beam, and a pair of sub beams, which is a positive first-order light beam and a negative first-order light beam each having a polarization direction perpendicular to a polarization direction of the main beam. Accordingly, it is possible to prevent the reflected sub beams from a recording layer, which is a target undergoing recording and/or reproducing, from interfering with the reflected main beam from a recording layer, which is a non-target not undergoing the recording and/or reproducing. Therefore, it is possible to obtain an accurate control signal based on the sub beams, and also possible to realize an optical pickup device having a preferable recording performance.

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patent: 06036374 (1994-02-01), None
patent: 2001-307351 (2001-11-01), None
patent: 2007-172793 (2007-07-01), None

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