| 摘要 |
PROBLEM TO BE SOLVED: To provide a shape measuring device resistant to temperature change and capable of performing a precise measurement. SOLUTION: This shape measuring device comprises a frame 3 for retaining a measuring object 5; a reference mirror 4 provided on the lower surface thereof, an XY stage 6 for moving the frame 3 in X and Y directions; and a displacement gauge 19 for measuring the Z-directional displacement of the measuring surface of the object 5. The displacement gauge 19 comprises a laser 1 for emitting measuring light and reference light beams differed in frequency whose polarizing directions are mutually orthogonal; a polarization beam splitter 21 for separating the beam to the measuring light beam and the reference light beam; a measuring optical system for passing the measuring light beam; a reference optical system for passing the reference light beam; a polarization beam splitter 24 for coupling the measuring light beam to the reference light beam; and a beat frequency detection system for detecting the beat frequency of the coupled light. The measuring optical system and the reference optical system have optical paths extending substantially in the same layout, and the optical path lengths of the both are substantially the same.
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