| 摘要 |
PROBLEM TO BE SOLVED: To measure the state of an incidence plane in a built-up state by radiating a coherent beam on the specified diameter position of a measured surface in a rotated state of an optical axis of a measured optical system, and obtaining the surface shape of the diameter from the measured data with the the reflected light of the coherent beam from the measured surface made to interfere. SOLUTION: Laser beams 2 emitted from a laser light source 1 are made two frequency light beams 4, 5 which are coherent beams orthogonal to each other in polarization bearings by a frequency shifter 3. The beam 4 transmitted through a polarized beam splitter 7 is converted into circularly polarized light by aλ/4 plate 23, travels toward a polarizing mirror 12 via a zoom lens 10 and enter vertically to a specified diameter of a measured surface 16 by the control of an arithmetic measuring means 34. The beam 4 is made incident on and reflected from by a wave front matching the curvature of the measured surface 16, returns through the same path so as to be transmitted again through the zoom lens 10, made linearly polarized light by theλ/4 plate 23 and recombined with the beam 5. After passing a polarizing plate 21, two frequency light beams 4, 5 interfere and are detected by a light receiving element 22 to obtain light path length difference from the phase difference.
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