| 摘要 |
PROBLEM TO BE SOLVED: To detect a focusing error signal and a tracking error signal by sufficiently suppressing T/F cross talk. SOLUTION: This sensor system is provided with a hologram element bisecting a reflection laser beam from an optical disk and generating a de-focus in the positive/negative directions related to an optical axis on the bisected beams and a pair of photosensors 13, 14 receiving the bisected beams. In such a case, a pair of photosensors 13, 14 are respectively divided to three parts by two pieces of first division lines 13F, 14F parallel to each other, and are provided with light receiving areas having a prescribed angleβwith the first division lines 13, 14 and bisected by second division lines 13T, 14T passing through the centers of the photosensors 13, 14. The angleβis in the range of 0 deg.<|β|<90 deg.. The focusing error signal is obtained, based on the outputs of the light receiving areas divided to three parts by the first division lines 13F, 14F, and the tracking error signal is obtained, based on the outputs of the light receiving areas bisected by the second division lines 13T, 14T.
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