Optical pickup device and optical disc device with offset...

Details Optical pickup device and optical disc device with offset... Optical pickup device and optical disc device with offset...

2011-08-16

2011-08-16

Simpson, Lixi C (Department: 2627)

Dynamic information storage or retrieval

With servo positioning of transducer assembly over track...

Optical servo system

C369S112010, C369S112030, C369S112100, C369S053230

Reexamination Certificate

active

08000184

ABSTRACT:
When first-order diffracted beams leak into a region, which is for receiving only a zeroth-order diffracted beam from an optical disc, due to positional displacement between an objective lens and a hologram element, an offset compensation signal includes an AC component, the offset compensation signal preferably including a DC component only. Accordingly, there may be caused deterioration in a modulation degree of the tracking error (TE) signal. A partial light shielding element110is formed on a hologram surface112aalong boundaries between a light receiving region (121a), which receives a zeroth-order diffracted beam, and light receiving regions (121b, 121c), which receive the zeroth-order diffracted beam and first-order diffracted beams, so as to cover the light receiving region (121a). Further, the partial light shielding element110shifts phases of transmitted light beams by π, whereby the TE signal is offset-compensated, and the modulation degree can be improved.

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International Search Report for corresponding Application No. PCT/JP2008/001008 mailed Jul. 29, 2008.
Form PCT/ISA/237.

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