| 摘要 |
<P>PROBLEM TO BE SOLVED: To solve the problems that a signal output decreases and S/N of the signal detection decreases in a conventional optical pickup device branching a detection beam into two beams and the conventional pickup device including a polarization HOE or a liquid crystal active rotator is expensive. <P>SOLUTION: A first-order diffracted light reflected from a first recording layer of an optical disk to be reproduced and diffracted by a diffraction type optical element converges to light-receiving cells 10A-10F of a photodetector as shown by 40a-40f. The other order light diffracted by the diffraction type optical element (including 0th-order diffracted light) becomes crosstalk light. The 0th-order diffracted light and -1st order diffracted light forms a spot near the light-receiving cells 10A-10F. The -1st order diffracted light 42a-42c from the first recording layer does not reach the light-receiving cells 10A-10F. The light reflected from a second recording layer and diffracted by the diffraction type optical element also becomes crosstalk light 44a-44f, so as not to reach the light-receiving cells 10A-10F. <P>COPYRIGHT: (C)2008,JPO&INPIT |
