Sony Magnescale Inc.

Hideaki Tamiya

A fixed point detecting device comprises a light source, a hologram disposed therebelow and having two portions, and two light receivers for detecting lights diffracted by the two portions of the hologram, wherein an angle of diffraction of light diffracted by one of the two portions of the hologram and an angle of diffraction of light diffracted by another of the two portions of the hologram have opposite signs and the same absolute value and are constant along the axis of measurement, and a difference in luminous intensity is great between positive and negative homogeneous lights diffracted by the two portions of the hologram.

Fixed point detecting device using detection of light diffracted by

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 use of the same light paths.

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Yamato, Japan

Hideaki Tamiya