| 摘要 |
A variable attenuator is provided for selectively attenuating a radiation beam in a lithographic apparatus. The attenuator is generally planar and comprises two wedge shaped prisms formed of refractive material located adjacent to each other, arranged so that the radiation beam passes through both prisms. The attenuator is rotatable to vary the angle at which radiation strikes the prisms, thus varying the transmission at each surface.
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