| 摘要 |
PROBLEM TO BE SOLVED: To provide a small and simple device for collectively detecting a plurality of stable phase-difference signals. SOLUTION: The laser beam from a coherent light source is bisected by an optical probe polarizing prism, the phase of wave front of an optical flux through each optical path is modulated and the wave fronts are duplexed as orthogonal and linear polarization, which is reflected at non-polarizing beam splitter, and amplitude-split into four equivalent optical fluxes by a quadrisecting diffraction grating 27 after passing through an opening board. The optical fluxes transmit different parts of a quartz plate 28 which is partially etched in advance to provide four steps, and 45 deg. polarization component is taken out of each transmission optical flux with a polarizing plate 29 so that each interference optical flux is detected in four regions 30a-30d of a light receiving element 30 to provide four phase-difference signal.
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