Optical Pickup Unit and Optical Disk Apparatus
AssigneesSanyo Electric Co., Ltd., Sanyo Optec Design Co., Ltd.
InventorsRyouichi Kawasaki, Yoshitaka Hotta
Life of this patent
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Abstract
An optical pickup unit comprises a diffraction grating that divides light into at least three luminous fluxes and condenses the three luminous fluxes to apply at least three focusing spots, independent of each other, onto a signal side of a medium. The diffraction grating is divided into at least four regions, a first region, a second region, a third region, and a fourth region.
Claims18
An optical pickup unit comprising a diffraction grating that divides light into at least three luminous fluxes, the optical pickup unit condensing the three luminous fluxes to apply at least three focusing spots, independent of each other, onto a signal side of a medium, the diffraction grating being divided into at least four regions, a first region, a second region, a third region, and a fourth region.
The optical pickup unit of clam 1, wherein
- the second region and the third region are disposed between the first region and the fourth region, and wherein
- a periodic structure of the second region is a periodic structure having a phase differing by about 120 degrees from that of a periodic structure of the first region,
- a periodic structure of the third region is a periodic structure having a phase differing by about 60 degrees from that of the periodic structure of the second region;
- and
- a periodic structure of the fourth region is a periodic structure having a phase differing by about 120 degrees from that of the periodic structure of the third region.
Dependencies are inferred from the claim text.