| 摘要 |
PROBLEM TO BE SOLVED: To provide a position error signal detection device capable of generating an in-plane position error signal showing positional deviation of a light collection spot without causing an off-set.SOLUTION: An optical recording medium 3 includes a beam guide layer having a two-dimensional periodic rugged structure. A diffraction optical element 17 generates a main beam, a first sub beam group deflected symmetrically with respect to the main beam in a first direction, and a second sub beam group deflected symmetrically with respect to the main beam in a second direction. A photodetector 11 receives reflection light from the optical recording medium 3. An error signal generation circuit generates a first in-plane position error signal showing positional deviation in the first direction of a light collection spot of the main beam on the basis of reflection light of the main beam and reflection light of the second sub beam group. In addition, the error signal generation circuit generates a second in-plane position error signal showing positional deviation in the second direction of the light collection spot on the basis of the reflection light of the main beam and reflection light of the first sub beam group. |
