| 摘要 |
<P>PROBLEM TO BE SOLVED: To determine whether a desired layer is subjected to focus servo even when layer identification information is not recorded in each of recording layers. <P>SOLUTION: On the basis of a drive signal component of a focus actuator obtained when focus servo control is on, a transmission function of the focus actuator and a focus error signal obtained when the focus servo control is on, a displacement signal is generated that shows the amount of displacement in the focus direction of a lens (focus lens) to be driven by the focus actuator to vary the focusing position of the light, to extract a low frequency component of the displacement signal. The low-frequency component of the displacement signal is extracted to obtain an offset of the focus lens for layer selection. On the basis of the low frequency component of the displacement signal, whether the desired layer (where data are recorded or reproduced) is subjected to focus servo. <P>COPYRIGHT: (C)2011,JPO&INPIT |
