| 摘要 |
PROBLEM TO BE SOLVED: To reduce noise caused by reflections from wall surfaces of a beam splitter disposed within an interferometer in order to branch or unify measurement light flux. SOLUTION: The measurement light flux passes through four wall surfaces a, a', b, and b' among the wall surfaces of the beam splitter 15. Angles formed by the four wall surfaces with a semi-transparent surface 15C are set at equal values different from 45°. Using such a beam splitter 15 having wall surfaces with angles different from 45°reduces noise superimposed on a measurement signal of an interferometer owing to reflections from the wall surfaces a, a', b, and b'. Since the angles have values equal to each other, relative configurations of respective optical elements on the periphery of the beam splitter are kept from being complicated. COPYRIGHT: (C)2005,JPO&NCIPI
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