| 摘要 |
A device reads and/or records marks in a track on a record carrier via near field optical recording. The device has a head including a lens to be positioned at a near field distance from a surface of the record carrier. An air gap controller is for controlling an air gap (81) between the lens and the surface, and has an approach mode for bringing the lens from a remote distance in the far field to the near field distance. Thereto the controller provides an increasing periodical excitation signal (83) for generating a sequence of approach instants at which the lens approaches the surface. At the approach instants the lens has substantially zero velocity (84). The sequence of approach instants brings the lens subsequently closer to the surface. When the lens enters in the near field range at one of the approach instants, the air gap controller is switched to closed loop mode. The periodical excitation (83) is synchronized to the rotation of the record carrier such that the approach instants correspond to a minimum of the disc displacement (82). |
