| 摘要 |
PURPOSE:To detect two-dimensional displacements with one piece of a reading head by interfering the diffracted light generated by two-dimensional diffraction gratings and detecting the interference fringes through slits with respect to the components of the respective X-, Y-directions. CONSTITUTION:The light from a coherent light source 1 is passed through a polarizing cube prism 2 and is irradiated through a 1/4 wavelength plate 3 and a lens L2 to two-dimensional diffraction gratings 4 having fringes in X-, Y-directions. The reflected light from the gratings is formed an image through a removing filter 5 for 0 order diffracted light whereby two-dimensional difraction grating images 6 are obtained. The images 6 are passed through slits 7 provided in the respective X-, Y-directions, and is subjected to photometry with a photodetecting means 8. The slits differing in phase by each 90 deg. with respect to the X-, Y-components are provided, and the displacements in the X-, Y-directions of the gratings 4 are operated from the corresponding photometric outputs. |
