| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an optical head having a diffraction element which is capable of improving the quality of a TE signal by a DPP method even when light amounts of two sub-spots are unbalanced with respect to optical disks having different groove pitches. <P>SOLUTION: In a three-beam optical head, the diffraction element 12 is divided in a radial direction of the optical disk into a first area 31, a second area 32, and a third area 33, wherein the second area 32 is further divided into a fourth area 321 and a fifth area 322. A periodic structure of the first area 31 is displaced from that of the fourth area 321 just by 1/4 period, a periodic structure of the third area 32 is displaced from that of the first area 31 just by 1/2 period, and a periodic structure of the fifth area 322 is displaced from that of the third area 33 just by 1/4 period and from that of the fourth area 321 just by 1/2 period. <P>COPYRIGHT: (C)2008,JPO&INPIT |
