| 摘要 |
An optical head for scanning a dual-layer disk includes a polarising beam splitter for splitting an input beam ( 7 ) from a single radiation source to form two separate, orthogonally polarised beams ( 9, 10 ). One of the beams is passed trough a fixed collimator lens ( 13 ), whilst the other is passed trough a movable collimator lens ( 21 ). The beams are directed along a common beam path through a common objective lens ( 17 ) which is itself movably mounted. Focusing and terror correction is provided separately for each layer when scanning the two layers by actuation of the objective ( 17 ) and movable collimator ( 21 ), respectively. The use of a single radiation source and a single objective provides a reduction in the number of components, and the complexity of components, required to read a dual-layer disk.
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