| 摘要 |
Optical scanning device for scanning an information plane (1a) of a disc-shaped optical recording medium (1) having an outer surface (1b) extending parallel to the information plane. The scanning device comprises a radiation source (7) for supplying a scanning beam (7a), and an optical scanning unit which comprises a lens system for focusing the scanning beam to a scanning spot (7b) on the information plane. The lens system has an optical axis (9) and comprises a first lens unit (9a) with a first lens (9a1) having an entrance side (11) and an exit side (13), and a second lens unit (9b) with a second lens (9b1) situated opposite the exit side of the first lens. The scanning unit also comprises a drive means for displacing the first lens along the optical axis and an adjusting means for adjusting the second lens with respect to the recording medium. To inhibit spherical and/or comatic and/or astigmatic aberrations during scanning, the adjusting means comprises a rotatably driven rotation element (15) which forms part of the second lens unit, is journaled in a stationary element (17) and has a disc-shaped surface (15a) provided with a pattern of grooves for cooperation with the outer surface of the recording medium. |
