| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an optical disk device precisely discriminating whether the focus servo is applied to the cover layer and each signal layer of a multilayer optical disk. <P>SOLUTION: In the optical disk device, when a multilayer optical disk 10 having a plurality of signal layers laminated is recorded and reproduced, the position of a collimator lens in an optical means 20 in the direction of the optical axis is aligned to an optimum position where the amplitude of the focus error signal is maximized for each signal layer, thus correcting spherical aberration and setting the amplitude of the tracking error signal in other signal layers to nearly 0. As a result, the tracking error signal is checked by switching a collimator lens position, so that the signal layer currently in focus servo state is specified. In the focus servo state, when tracking error signals not less than a threshold are not detected in all signal layers, it is determined that the cover layer is focus-servo controlled. <P>COPYRIGHT: (C)2008,JPO&INPIT |
