| 摘要 |
PURPOSE:To enable one fixed reflecting mirror to be shifted under control without directly mounting a shifting means to the mirror, by providing n-1 reflecting mirrors forming an annular light path with shifting means for moving them in the normal direction and providing the other mirror with a strain generator means for shifting the other and fixed mirror with respect to the n-angular path. CONSTITUTION:First and second reflecting mirrors 15 and 16 are provided with separate shifting means for example of piezoacutuators 24 and 25, respectively, for shifting them under control in the normal direction, while no shifting means is provided for shifting them in the tangential direction. A strain generator means 30 instead is provided on a glass block 11. The strain generator means 30 has a deforming material 31 formed of a piezoelectric material for example and electrodes 32 and 33 are mounted to be opposed to each other on the surface of this piezoelectric material faced to a third reflecting mirror 17 and to an electric discharge path 12, respectively. When a voltage is applied between the electrodes 32 and 33, the distance of the piezoelectric material between the electrodes is changed. The glass block 11 is thereby deformed toward the third reflecting mirror 17, and the third reflecting mirror 17 is shifted in the direction normal thereto. |
