| 摘要 |
A method and apparatus involve: using beam influencing structure to cause a converging beam of radiation to propagate along a first portion of a path of travel; supporting an optical part so that the path of travel extends through the optical part, the converging beam arriving at the optical part along the first portion of the path of travel, and the path of travel having a second portion along which the converging beam travels away from the optical part; and selectively tilting the optical part about a pivot axis lying in an imaginary plane extending transversely to the first portion of the path of travel, pivotal movement of the optical part about the pivot axis causing a change in the orientation of the second portion of the path of travel with respect to the first portion thereof.
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