| 摘要 |
An optical scanning device ( 1 ) for scanning an information layer ( 4 ) of an optical record carrier ( 2 ), the device ( 1 ) comprising a radiation source ( 11 ) for generating a radiation beam ( 12, 15, 20 ) and an objective system ( 18 ) for converging the radiation beam on the information layer, the information layer being covered by a transparent layer ( 3 ) of thickness td and refractive index n<SUB>d</SUB>. The objective system comprises a lens formed of a single material. The lens satisfies the condition: Fomula (I), where t is the thickness of the lens, FWD is the free working distance between the lens ( 18 ) and the carrier ( 2 ), where t, td and FWD are expressed in millimeters, and where FWD+t<SUB>d</SUB>/n<SUB>d</SUB><0.51.
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