| 摘要 |
PURPOSE:To enable the position of a phase plate to be easily adjusted with a high accuracy by making the phase plate freely rotatable in a plane wherein the phase plate orthogonally intersects a rotating shaft. CONSTITUTION:A phase plate 1 is formed in an approximate L-shape in a plane and so arranged as to be parallel to a code wheel 3 that rotates with a discoid rotating shaft 1. Being pivotally supported in the constant position of a cylindrical casing 8 with the end of an arm forming the L-shape, the phase plate 7 is freely rotatable about an axial fulcrum 9. A detecting slit portion 6 is formed in a position corresponding to the slit 2 of the code wheel 3 on the arm of the phase plate 7 on the side of the axial fulcrum 9. The phase plate 7 is rocked about the axial fulcrum 9 by operating a operating portion 10 and the position of the detecting slit portion 6 relative to the slit 2 of the code wheel 3 is adjusted. Thus, the detecting slit portion 6 can be adjusted to an optimum position, resulting in a correct position adjustment.
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