| 摘要 |
<P>PROBLEM TO BE SOLVED: To satisfy to accurately control both of focusing and tracking. <P>SOLUTION: The photodetector 18 receives +first order diffracted light through a polarization hologram element 17. In the photodetector 18, a light receiving area for focus error signal generation and a light receiving area for tracking error signal generation are formed. The light receiving area for the tracking error signal generation is formed in a radial direction to the light receiving area for the focus error signal generation. Focus control is performed by using a double knife edge method, and tracking control is performed by using a DPP (Differential Push-Pull) method by 3 beams. In defocusing, diffused light is not mixed in the light receiving area for the tracking error signal generation since it is diffused in a tangential direction, and the tracking control is accurately performed. <P>COPYRIGHT: (C)2007,JPO&INPIT |
