Method of and apparatus for optically measuring displacement

摘要

The magnitude of displacement of an object to-be-measured is measured by projecting light beams on the object to-be-measured and a reference plane and utilizing the interference of lights reflected therefrom. The reflected lights from the object to-be-measured and the reference plane have their phase difference changed cyclically and forcibly. The discontinuous change of the magnitude of phase shift at the moment at which the phase difference of the two reflected lights caused by the displacement of the object to-be-measured has been compensated, and the magnitude of displacement of the object to-be-measured is found from the counted result of the discontinuous changes and the magnitude of phase shift at the moment at which the phase difference has been compensated.