Dynamic information storage or retrieval – Condition indicating – monitoring – or testing – Including radiation storage or retrieval
Reexamination Certificate
2005-05-10
2005-05-10
Tran, Thang V. (Department: 2653)
Dynamic information storage or retrieval
Condition indicating, monitoring, or testing
Including radiation storage or retrieval
C369S059170
Reexamination Certificate
active
06891787
ABSTRACT:
A defect detecting circuit generates a defect detection signal when the level of a sum signal obtained from an optical sensor in an optical pickup is lower than a predetermined level, and a gate circuit responds to the defect detection signal to set the level of a fine clock mark signal to zero, that is a difference signal obtained from the optical sensor in the optical pickup. A fine clock mark is thus distinguished from any defect such as scratch and a correct fine clock mark signal is accordingly generated. Alternatively, the value of a sum signal, which indicates the total amount of reflected light output from the optical pickup, is compared with a predetermined threshold. When the period in which the value of the sum signal is smaller than the threshold lasts for a predetermined threshold time period, it is determined that focus of an objective lens deviates from an optical disk and accordingly focus servo control is stopped. The threshold is defined by gradually reducing a drive signal while detecting peak and bottom values of the sum signal which is generated as the objective lens is moved in the direction of its optical axis, and then setting the threshold between the detected peak and bottom values. In this way, defocus of the objective lens is surely detected.
REFERENCES:
patent: 5062091 (1991-10-01), Maeda et al.
patent: 5526332 (1996-06-01), Yamada et al.
patent: 6359848 (2002-03-01), Van Den Enden
patent: 6388954 (2002-05-01), Awano et al.
patent: 60-131639 (1985-07-01), None
patent: 5-89492 (1993-04-01), None
patent: 8-203108 (1996-08-01), None
Sanyo Electric Co,. Ltd.
Tran Thang V.
Vuong Bach
Westerman Hattori Daniels & Adrian LLP
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