| 主权项 |
1. Optical apparatus, comprising:
a laser-resonator terminated by first and second mirrors; a gain-element within the laser-resonator; a source of optical pump-radiation arranged to deliver optical pump-radiation to the gain-element thereby causing a beam of laser-radiation to circulate in the laser-resonator between the first and second end-mirrors along a beam-path, the beam path being normally incident on the first and second mirrors at corresponding first and second incidence points; a plurality of beam-translation mirrors located within the laser-resonator in beam-path, the beam-translation mirrors being spaced apart in a fixed relationship with each other, with the laser-radiation beam incident on each of the beam-translation mirrors at an acute angle of incidence, the plurality of beam-translation mirrors being selectively rotatable as a group about at least a first axis, with the laser-radiation beam making an even number of reflections from the beam-translation mirrors; and wherein the selective rotation of the plurality of beam-translation mirrors selectively changes the incidence angle of the laser-radiation beam on each of the plurality of beam-translation mirrors thereby selectively translating the second incidence point on the second end-mirror, while maintaining normal incidence of the beam path on the second end-mirror. |
