| 摘要 |
PROBLEM TO BE SOLVED: To reduce restriction on an optical component used for a projection lens. SOLUTION: This system for acquiring positional information related to a specific axis 42 includes a movable device 36, an interferometer, and beam-steering members 64 and 66. In the movable device 36, having first and second reflecting faces 40 and 42 on side faces parallel to the specific axis 32, the first reflection face 40 is angled to the second reflection face 42 by a certain angle, and the first and second reflecting faces 40 and 42 are not parallel to the specific axis 32. The interferometer, directing a second beam 46 so that it strikes the second reflection face 42, is provided with a beam coupler 50 positioned to a detector 52. The beam steering members 64 and 66 are arranged to the interferometer and the first and second reflecting faces 40 and 42 for performing operation so that the first and second beams 44 and 46 reach the beam coupler 40, without having beam path segment that varies its length according to the movement of the movable device 36 along the specific axis 32. COPYRIGHT: (C)2005,JPO&NCIPI |
