| 摘要 |
PURPOSE:To measure a three-dimensional surface shape with high accuracy by turning an optical element which performs shearing operation in two orthogonal direction by rotating mechanisms. CONSTITUTION:Two rotating mechanisms 70 each consisting of a cylindrical spindle holder 72 having a internal screw 71 at part of the inner peripheral surface, a spindle 74 having an external screw 73 engaging the internal screw, etc., are arranged for a total reflecting element. When the object surface is measured, the mirror 59 is rotated around a Z axis by a desired angle to shift the optical axis of reflected light from a beam splitter laterally and interference fringes are observed. Then, the mirror 59 is rotated around a Y axis to make a lateral shift and interference fringes are observed. Then, the residual aberrations are removed from data on those both interference fringes and a fringe analysis is taken to compute the three-dimensional shape of the object surface. Thus, the shear direction is known easily and accurately by turning the mirror in the two directions and the angle of turning of the mirror 59, i.e. shear quantity is know easily and accurately from the movement extent of the spindle 74.
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