| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an optical head device for generating a satisfactory reproduction signal at a low cost. <P>SOLUTION: The optical head device includes a semiconductor laser element 30, a photodetector 40, and a hologram element 20. In a first diffraction region 261a of the hologram element 20, a grating pattern having coma aberration in a direction X in first and second light receiving regions 451a and 451b, and converting return light from an optical disk 10 into incident light, is formed across a second light receiving division line L72 of a first light receiving region group 451. In a third diffraction region 262a, a grating pattern having coma aberration opposite to the polarity of the first diffraction region 261a in third and fourth light receiving regions 452a and 452b, and converting return light from the optical disk 10 into incident light, is formed across the second light receiving division line L72 of a second light receiving region group 452. <P>COPYRIGHT: (C)2011,JPO&INPIT |
