| 摘要 |
An optical focussing device for focussing a radiation beam on a record carrier, more particularly for focussing a light beam on a video record, the objective being included in an electronic position control system with the aid of an electromagnetic drive system by which it can be moved parallel to its optical axis. The parallel guide for the objective consists of a cylindrical bearing bush which is connected to the frame of the device, in which bush the lens mount of the objective is an accurate axially slidable fit. The lens mount preferably has an outer surface of opalized aluminium and the bearing bush an inner surface which contains PTFE.
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