| 摘要 |
<P>PROBLEM TO BE SOLVED: To make it possible to generate a good differential push pull signal DPP even in two-layer optical recording medium without need of change in light receiving pattern of a photodetector and to carry out tracking control normally. <P>SOLUTION: When tracking signal detection by a differential push pull method using three beams is applied to two-layer optical recording medium, for example, even if there is a return light from another layer (a second layer) which is not an object layer (a first layer) to which recording or reproduction is performed, a bias of a push pull signal in a sub-beam does not fluctuate by selection and use only of a push pull signal G-H by a sub beam of one side, and stable tracking control is enabled by generating a good differential push pull signal DPP1=(C-D)-k1×(G-H). When the second layer is used as an object layer, it is enough to select and use only of the good differential push pull signal E-F by the sub beam, and to generate a differential push pull signal DPP2=(C-D)-k2×(E-F). <P>COPYRIGHT: (C)2005,JPO&NCIPI |
