| 摘要 |
In an instrument and method for optically measuring a displacement of a scale which can achieve the noise elimination of returning light to a coherent light source, the scale and optical system are so constructed that an intersecting point of light fluxes radiated from the coherent light source and split into those fluxes by means of a first beam splitter is not present on a transmitting type diffraction grating and the incident lights (d, e) on a reflecting plate and the reflected lights (f, g) from the reflecting plate have no common pass the same light paths. <IMAGE> |
