| 摘要 |
PROBLEM TO BE SOLVED: To improve the fringe scan precision by, in a lattice-projection type moire device provided with a fringe scan function, providing a specified fixed lattice near a projection lattice to form a moire stripe, and calculating the movement amount of the projection lattice through utilization of change of the moire stripe. SOLUTION: A fixed lattice 102 of the same pitch as a projection lattice 40 is provided at a crossing angle 5 deg. near the projection lattice 40 of a projection optical system. The moire strip formed by both lattices changes according to movement of the projection lattice 40, so by detecting the change, the movement amount of the projection lattice 40 is calculated. The change in moire stripe is detected through detection of the illuminance of moire strip using a photo cell 104 provided near the fixed lattice 102.
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