| 摘要 |
<p>Optical apparatus for scanning a beam across and object field comprising, a source of radiation (21, 22, 23) for providing a beam (15) of said radiation, first moveable reflective means (11A), first optical means (26) for passing said beam to said first moveable reflective means (11A) so that said beam is reflected from said first moveable reflective means (11A), reflective means (28) to reflect said once reflected beam a second time to said first moveable reflective means (11A) where it is reflected a third time, second optical means (24, 26, 31, 32, 33) to pass said thrice reflected beam (15E) from said first moveable reflective means (11A), to a second moveable reflective means (11B) whereby said beam is reflected and is scanned along a focus line, the optical path length between said first (26) and second optical means (24, 26, 31, 32, 33) being variable as said first moveable reflective means (11A) moves, whereby to provide a variable distance from said second moveable reflective means (11B) to said focus line.</p> |
