| 摘要 |
A positioning apparatus includes first and second stages, a pair of first mirrors having reflective surfaces disposed on the first stage at an acute angle with a vertical axis, a pair of second mirrors disposed on the second stage and having reflective surfaces orthogonal to the vertical axis, a reference structure functioning as a reference for measuring the vertical position of the second stage, a pair of third mirrors disposed on the reference structure and having reflective surfaces orthogonal to the vertical axis, and a pair of interferometers for measuring the vertical position of the second stage using the first, second, and third mirrors.
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