Multilayer optical disc
AssigneeHitachi Consumer Electronics Co., Ltd.
InventorsYoshinori ISHIKAWA, Harukazu MIYAMOTO, Akemi HIROTSUNE
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Abstract
A multilayer optical disc which has three or more recording layers and enables easy positioning of a focused beam spot onto a particular recording layer in which a BCA is disposed. An inter-layer distance between a particular recording layer and a recording layer adjacent to the particular recording layer is larger than the other inter-layer distances in which, at the focused beam spot positioning, the focused beam spot traverses the said adjacent recording layer earlier than the other recording layer adjacent to the particular recording layer.
Claims5
1-8. (canceled)
A multilayer optical disc having three or more recording layers having a structure in which:
- reflectance of each of the recording layers is substantially constant, both a first recording layer in which information to be reproduced has been stored and a second recording layer adjacent to the first recording layer being provided, wherein:
- an interlayer distance between the first recording layer and the second recording layer is larger than other interlayer distance.
A focus drawing method for irradiation of a laser beam to a multilayer optical disc having a three or more recording layers, thereby recording/reproducing information, the multilayer optical disc having a structure in which reflectance of each of the recording layers is substantially constant, both a first recording layer in which information to be reproduced has been stored and a second recording layer adjacent to the first recording layer being provided, an interlayer distance between the first recording layer and the second recording layer being larger than other interlayer distance, comprising the steps of:
- correcting a spherical aberration at the first recording layer;
- traversing an objective lens in a direction of thickness of the multilayer optical disc;
- detecting a focus error signal in each of the layers of the multilayer optical disc;
- and
- drawing a focus to the first recording layer based on the focus error signal.
Dependencies are inferred from the claim text.