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    • 8. 发明专利
    • AT411594T
    • 2008-10-15
    • AT04769759
    • 2004-10-29
    • KONINKL PHILIPS ELECTRONICS NV
    • VAN DER LEE ALEXANDERBUSCH CHRISTOPHER
    • G11B7/09G11B7/085G11B7/135G11B7/14
    • The present invention relates to an optical scanning device for reading out from or writing on an information carrier. Said optical scanning device comprises a radiation source for producing a radiation beam, means for dividing the rad i tion am infordation calriero sub-beams, focusing means for focusing the plurality of spots on said information carrier, which reflects said plurality of radiation sub-beams towards a detection branch and focus error detection means for detecting a focus error signal. Said focus error detection means comprise on said detection branch, a servo lens for focusing the reflected radiation sub-beams onto a focus plane, a spatial filter for isolating a reflected radiation sub-beam at the focus plane and a split detector for detecting a focus error signal from the isolated radiation sub-beam. The focus error detection means further comprise decision sub-means for deciding whether the focus error signal can be used to correct a position of the focusing means.