| 摘要 |
An optical apparatus is disclosed that has a convex mirror and a concave mirror with an aperture, wherein, in use, radiation from a radiation emitter passes through the aperture and is incident upon the convex mirror before being incident upon the concave mirror, the optical apparatus arranged to form the radiation into a radiation beam, wherein the concave mirror is translatable towards and away from the convex mirror or the convex mirror is translatable towards and away from the concave mirror, to adjust divergence of the radiation beam.
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