| 摘要 |
PROBLEM TO BE SOLVED: To provide a read-only optical disk device which reproduces a multilayer optical disk stably. SOLUTION: A read-only device reproduces the multilayer optical disk having a first layer and a second layer. In focus search, a comparator 10 compares the DC level of an RF sum signal with a first threshold, and a comparator 12 compares an RF signal level with a second threshold. When both of the DC level of the RF sum signal and the RF signal level are not lower than the respective thresholds, focus-in is performed, and a comparator 14 compares the RF signal level after focus-in with a third threshold. Only when the RF signal level after focus-in is not lower than the third threshold, tracking servo is performed, so that overrun of the tracking servo in an unrecorded layer is prevented. COPYRIGHT: (C)2008,JPO&INPIT
|
