| 摘要 |
PROBLEM TO BE SOLVED: To obtain an optical pickup device in which servo signals are generated by receiving all first-order diffracted light beams, that are diffracted by a diffraction element, through a light receiving element and a good tracking control is conducted without introducing an offset in servo signals. SOLUTION: The light beams from a light source are separated into zero- order and±1st-order light beams by a first diffraction element and a main spot (S1) and two subspots (S2 and S3) are formed on a magneto-optical disk by 0-order and±1st-order light beams through an optical system. Diffraction patterns S1', S2' and S3' by these reflected light beams are formed on a second diffraction element 3 and received by a light receiving element 10. The element 3 is bisected into regions (21+22) and (23+24) in the radial direction of a magneto-optical disk and moreover, bisected into regions (21+23) and (22+24) in the track direction. The diffracted light beams from these regions by the diffraction patterns are all made incident on a light receiving element 10. Thus, the servo signal without having an offset is obtained by computing the light receiving element outputs of each spot. Note that a stable tracking control signal is obtained through the generation of the servo signal with the beam light quantity that is twice the quantity of a conventional case.
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