| 摘要 |
An apparatus for varying the vergence of a beam of light from a laser including first and second focusing reflector means; one for receiving the beam of light and another for directing it away from the apparatus in a predetermined direction. Intermediate the two focusing reflecting means, there is provided an arrangement of substantially flat surface reflector means, one of which is moveable for varying the length of the path of the beam of light through the apparatus. In accordance with a preferred embodiment, the two focusing reflecting means comprise parabolic mirrors and the moveable reflector means comprises a piston mirror.
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