| 摘要 |
<P>PROBLEM TO BE SOLVED: To detect a tracking error by optimizing a diffracted light intensity ratio to improve laser use efficiency in an optical pickup using optical beams of three different wavelengths. <P>SOLUTION: This pickup is provided with first to third emission parts for emitting optical beams of three different wavelengths, a diffraction optical element 4 which is provided with, in at least one surface, a diffraction part 4a provided with a first phase grating part 31a having a first phase height with respect to a reference surface and second phase grating parts 31b having second phase heights with respect to the reference surface in both sides of the first phase grating part 31a so as to have 2-stage phase heights, on which optical beams emitted from the first to third emission parts and matched with one another in optical axis are made incident, and which devides the first to third optical beams into three beams, an objective lens 7 for condensing the emitted optical beams on the signal recording surface of an optical disk 8, and a photodetector 10B for detecting return optical beams reflected on the optical disk 8. <P>COPYRIGHT: (C)2008,JPO&INPIT |
