Optical detection apparatus for detecting information relating to relative displacement of an object on whch a diffraction grating is formed

A driving system for driving an object in two directions, said system comprising:

• a driving unit for driving the object in two directions;
• a scale, provided on the object, and a diffraction grating formed on said scale in two axial directions with a predetermined pitch;
• a light-emitting device configured to emit a light beam;
• a first optical element configured to divide the light beam emitted from said light-emitting device and impinging on one area of said first optical element into a plurality of light beams directed in each of the two axial directions to said diffraction grating, wherein said diffraction grating diffracts said plurality of light beams in each of the two axial directions;
• a second optical element positioned and configured to receive and combine the plurality of diffracted light beams for each of the two axial directions by diffracting at least one of the diffracted light beams;
• a plurality of detection units, each configured to receive and detect the combined plurality of diffracted light beams for one of the two axial directions, and to output information relating to a relative displacement of the object in each of the two axial directions;
• and
• a control unit for controlling said driving unit based on the outputs from said plurality of detection units.

An apparatus for optically detecting information relating to a relative displacement of an object on which a diffraction grating, arranged in two axial directions with a predetermined pitch, is formed, said apparatus comprising:

• light source means for emitting a light beam;
• light beam dividing means for dividing the light beam emitted from said light source means and impinging on one area of said light beam dividing means into a plurality of light beams directed in each of the two axial directions to the diffraction grating on the object which produces a plurality of diffracted light beams for each of the two axial directions;
• light beam combining means for receiving and combining a plurality of diffracted light beams for each of the two axial directions from the diffraction grating formed on the object by diffracting at least one of the diffracted light beams;
• and
• detection means for detecting the combined diffracted light beams for each of the two axial directions, and for detecting information relating to a relative displacement of the object in each of the two axial directions.