| 摘要 |
The invention relates to an optical device comprising a first radiation source ( 101 ) for producing a first radiation beam, a second radiation source ( 101 ) for producing a second radiation beam and means for directing the first and second radiation beams along a common optical path. Each radiation beam has an intensity distribution, a central axis and an outer envelope. The optical device further comprises, in the common optical path, means ( 103 ) for modifying the intensity distribution of the first radiation beam only. This means are designed for increasing the ratio between the intensity near the envelope and the intensity near the central axis of the first radiation beam by reducing at least the intensity of the first radiation beam near its central axis.
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