发明名称 |
Defocus detection device, defocus detection method and optical disk unit using the same |
摘要 |
Defocus detection device and method capable of detecting a defocus accurately during recording of information to an optical disk having a plurality of recording layers and an optical disk unit using the device and method are provided. A temporal restriction is imposed on defocus detection and besides, in comparison with a level for detection of a first change of a focus error signal developing during a defocus, a level for detection of a successively occurring second change of a polarity inverse to that of the first change is made to be smaller. When the first level is exceeded and thereafter the second level is exceeded within a restricted time, a defocus is detected.
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申请公布号 |
US7542387(B2) |
申请公布日期 |
2009.06.02 |
申请号 |
US20050183085 |
申请日期 |
2005.07.15 |
申请人 |
HITACHI, LTD.;HITACHI-LG STORAGE, INC. |
发明人 |
ISHIKAWA YOSHINORI;SUZUKI MOTOYUKI |
分类号 |
G11B7/00 |
主分类号 |
G11B7/00 |
代理机构 |
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代理人 |
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主权项 |
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地址 |
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