| 摘要 |
A laser system generates a beam consisting of light of two wavelengths, one of which is in the visible spectrum. The light of the other wavelength is ultraviolet and is generated from the visible light as a harmonic of it. The ultraviolet light is focussed, by reflection only, onto a target. Most of the visible light is separated out of the beam by dichroic mirrors but a very small residue is allowed to illuminate the target so that the exact position at which the ultraviolet light impacts the target can be monitored by means of a microscope.
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