| 摘要 |
<P>PROBLEM TO BE SOLVED: To always stably detect a tracking control signal (TES) even in the case that a layer interval is different between a recording layer and a guide layer due to the difference of the recording layer to be an object in an optical information device corresponding to a grooveless multilayer disk in which a multilayer recording layer for recording and reproducing an information signal and a dedicated guide layer for detecting the TES are different from each other. <P>SOLUTION: A plurality of light spots for TES detection defocused from each other are irradiated on the guide layer by using a holographic diffraction grating. A TES is individually differently detected from the respective light spots, and the signal subjected to addition processing are used for tracking control to thereby expand a defocus dynamic range of TES detection remarkably. <P>COPYRIGHT: (C)2013,JPO&INPIT |
