| 摘要 |
<p>By means of a radiation beam, an apparatus writes or reads information on an information surface of a rotary optical information disc (21), which apparatus comprises an objective frame (16) on which an objective (17) for concentrating the radiation beam to a radiation spot is mounted by means of a parallel guide (19) in such a way that it can move in the direction of its optical axis (18). The objective is protected against dust, contaminants and mechanical damage by means of stationary plane-parallel radiation-transparent shielding means (22), which are interposed between the objective and the rotary information disc, the lens system of the objective being corrected for the optical properties of the shielding means.</p> |
