Encoding apparatus for making measurements of two-dimensional displacement of an object

摘要

An encoding apparatus includes: a light source; a diffraction grating, including a number of fine grating portions orthogonally arranged in columns and rows in a diffraction grating surface, for producing first diffracted light rays and second diffracted light rays in accordance with light emitted from the light source, each of the first diffracted light rays having a direction cosine on a first plane, and each of the second diffracted light rays having a direction cosine on a second plane; an interference unit for producing a first interference light ray by subjecting two diffracted light rays of the first diffracted light rays to interference, and for producing a second interference light ray by subjecting two diffracted light rays of the second diffracted light rays to interference; a first detection unit for detecting a phase change of the first interference light ray when an object is moved relative to the light source; and a second detection unit for detecting a phase change of the second interference light ray when the object is moved relative to the light source.