| 摘要 |
PROBLEM TO BE SOLVED: To provide a small optical pickup device capable of preventing the generation of unwanted stray light. SOLUTION: A second diffraction element 3 is divided into a first area 3a and a second area 3b by a dividing line DL passing through the optical axis, a part diffracted by the first area 3a among the main beams reflected by a disk is converged on the boundary between photodetectors 7b, 7c and a part diffracted by the second area 3a is converged on a photodetector 7d. By representing two sub-beams by a first and second sub-beams, a diffracted part of the first sub-beam in the first area 3a is converged on the photodetector 7a and the remainder is converged between photodetectors 7c and 7d. Similarly, a diffracted part of the second sub-beam in the second area is converged on the photodetector 7e and the remainder is converged between photodetectors 7c and 7d. A radial error signal based on a three beam method is generated by comparing the outputs of the photodetector 7a and the photodetector 7e with each other. |
