| 摘要 |
PURPOSE:To obtain stably a control signal and an optical information signal of an optical control system by providing a photodetecting surface on the peripheral part of a photodetecting surface of a square sectioned equally into 4-square as well. CONSTITUTION:In case a scatter 24 of light has been generated due to a distortion (caused by a flaw, dust, etc.) on the optical information surface, this scattered light 24 is photodetected by photodetecting surfaces 21, 22 of the peripheral part of photodetecting surfaces 17-20 of a square sectioned equally into 4-square, and an optical information signal is obtained by adding it to an output signal of the photodetecting surfaces 17-20 of the square as mentioned above. The optical information signal can be obtained stably by providing the photodetecting surfaces 21, 22 on the peripheral part of the photodetecting surfaces of the square as mentioned above, as well, photodetecting the scattered light 24 of an optical spot 23, and obtaining the output signal. Also, this scattered light 24 is scarcely received by the photodetecting surfaces 17-20 of the square as mentioned above therefore, even if the output signal obtained by the photodetecting surface of the square as mentioned above is used for a control signal of an optical control system, an influence of the scattered light 24 is scarcely exerted, and a stable control signal can be obtained.
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