| 摘要 |
A beam expander suitable for use with laser machining apparatus comprises a convex paraboloidal surface 7 and a concave paraboloidal surface 8 formed from a single metal element 10. The expander has an optional zoom facility provided by a plane mirror 12, moveable along an input-output axis, for altering the position of an incident beam on the convex surface 7 thereby altering the magnification of the system.
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