To provide a phase shift interferometer for measuring a height of a workpiece surface at high speed with high accuracy.
This phase shift interferometer is equipped with a lighting optical system 200, a non-interference light beam generation means 300, and a phase shift interference fringe acquisition part 400. The generation means 300 divides a beam from the optical system 200 into two light beams, that is, an illumination beam to the workpiece surface and an incident beam to a reference surface. Further, the generation means 300 combines a body beam from a workpiece W with a reference beam from the reference surface in a non-interference state into a non-interference light beam. The acquisition part 400 divides the non-interference light beam from the generation means 300 into three or more light beams. Then, the acquisition part 400 causes the body beam and the reference beam included in respective non-interference light beams obtained by the division, to interfere with each other with phases varying according to light beams obtained by the division, thereby obtaining interference fringes of different phases.
Kanji Nakayama
Tsuyoshi Ishizaki