| 摘要 |
<p>A light source (11) and a detector (17) are disposed on a side of a path of light travelling from a collimating optical system (12) to a movable mirror (14) through a BS (13) opposite to that on which a fixed mirror (15) lies, and at the same time, disposed on a side of a path of light travelling from the fixed mirror (15) to a light collecting optical system (16) through the BS (13) opposite to that on which the movable mirror (14) lies. With this, an optical arrangement in which the incident angle of the light entering the BS (13) from the collimating optical system (12) is less than 45° can be easily achieved while the light beams travelling along both the light paths are prevented from being obstructed by the light source (11) and the detector (17). Moreover, this optical arrangement ensures a large space on a side of the BS (13) opposite to that on which the light source (11) and the detector (17) are disposed, and a driving mechanism (21), for example, can be disposed in the space.</p> |
