| 摘要 |
PROBLEM TO BE SOLVED: To use a three-beam system with a DPD system, to increase the sensitivity of non-focusing detection, and to miniaturize an optical pickup by dividing returning light from an optical disk into two light paths, and applying specific astigmatism to the light of each divided light path. SOLUTION: A hologram element 8 has first and second hologram parts. The first hologram divides returning light into first and second light paths. The second hologram applies first astigmatism to the light of the first light path as first processing light, and applies second astigmatism at 90 degrees to the first astigmatism to the light of the second light path as second processing light. The first processing light enters a first detector 11 with four light reception parts, and the second processing light enters a second detector 12 with four light reception parts. A tracking error signal is obtained by an operation circuit being connected to the output side of a light detection part 9. |
