| 摘要 |
PURPOSE:To make it possible to measure the relative displacement of a plurality of objects with high accuracy, by providing a diffraction lattice on one object and measuring the phase of the diffracted wave obtained by diffracting a wave motion with the diffraction lattice. CONSTITUTION:Diffraction lattices G1, G1' each having the same cycle as a diffraction lattice G2 are arranged on object 1 at positions irradiated with a diffracted wave generated by diffraction lattice G2. The phase difference phi between the wave D diffracted by the diffraction lattice G2 and further diffracted by the diffraction lattice G1 to advance in the direction opposite to a direction I and the wave D' successively diffracted by the diffraction lattices G2, G1' is measured by detectors 4, 5. The phase difference phi is not dependent on the distance S between matters 1, 2 at all and proportional to the relative displacement (x) between the matters 1, 2 in the direction (x- direction) parallel to the surfaces of the diffraction lattices G1, G1', G2 and crossing the directions of the diffraction lattices at a right angle and phi=4pi.nmu/d(radian) is defined. This is an extremely simple result as compared with a case where the intensity of the wave D or D' is dependent on S or (x). Therefore, by measuring the phase difference phi, (x) can be measured regardless of S and the value of proportion coefficient S/d can be easily measured with high accuracy.
|
