| 摘要 |
PURPOSE:To enable highly accurate measurement simple to remove the effect of vibration or temp. change, by correcting the variation in the mutual lateral shifting distance between measuring light beams separated into two luminous fluxes incident to an area sensor in a real time. CONSTITUTION:An optical system consisting of a beam splitter 10 and flat mirrors 12, 14 splits measuring light into two luminous fluxes mutually inclined by a minute angle theta in an xy-plane predetermined in its advance direction. These two luminaus fluxes are incident to an area sensor 16 in a state laterally shifted by a minute distance S in the above-mentioned xy plane to generate an interference fringe on the sensor 16. This interference fringe is read by the sensor to receive Fourier transform. An inclination component is removed from the result of Fourier transform to receive inverse Fourier transform. Predetermined operation containing the integration in the lateral shift direction is applied to the phase difference known from the result of inverse Fourier transformation and the shape of a measuring wave front is obtained.
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