Position detection apparatus
AssigneeNippon Kogaku K. K.
InventorsNobutaka Magome, Yutaka Ichihara
Life of this patent
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Abstract
An apparatus includes a means for providing a predetermined frequency difference between two light beams and generating an optical beat with respect to interference between first and second diffracted light beams from a diffraction grating formed on a substrate, and a means for detecting a phase difference between the optical beat and a reference signal having a frequency corresponding to the frequency difference between the two light beams, and detects a position of the substrate based upon the phase difference in accordance with an optical heterodyne interference method.
Claims17
An apparatus for detecting a position of an article on which a diffraction grating is provided, comprising:
- means for emitting first and second coherent light beams radiated onto said diffraction grating, said first and second light beams having different frequencies, thereby generating an optical beat based on interference between diffracted light beams of said first and second light beams which are generated from said diffraction grating;
- means for producing a reference signal having a frequency corresponding to a frequency difference between said first and second light beams;
- and
- means, including means for detecting said optical beat, for comparing a phase of said optical beat with that of said reference signal.
An apparatus for detecting a position of an article on which a diffraction grating is provided, comprising:
- an apparatus main body;
- means for two-dimensionally moving said diffraction grating with respect to said apparatus main body within a plane including said diffraction grating;
- means for measuring a position of said article with respect to said apparatus main body during the two-dimensional movement;
- and
- means for detecting the position of said article based on a pitch of said diffraction grating,
- said detection means including:
- means for emitting first and second coherent light beams radiated onto said diffraction grating, said first and second light beams having different frequencies, thereby generating an optical beat based on interference between diffracted light beams of said first and second light beams which are generated from said diffraction grating;
- means for producing a reference signal having a frequency corresponding to a frequency difference between said first and second light beams;
- and
- means, including means for detecting said optical beat, for comparing a phase of said optical beat with that of said reference signal.
An apparatus for detecting a deviation in one direction between first and second diffraction gratings which have a periodicity in said one direction and are arranged on an identical plane to be parallel to each other, comprising:
- means for emitting first and second coherent light beams radiated onto said first and second diffraction gratings, said first and second light beams having different frequencies, thereby generating interference fringes, which scan said first and second diffraction gratings at a frequency corresponding to a frequency difference between said first and second light beams;
- means for producing a first alternative output having a frequency corresponding to the frequency difference based on a diffracted light beam generated from said first diffraction grating by said interference fringes;
- means for producing a second alternative output having a frequency corresponding to the frequency difference based on a diffracted light beam generated from said second diffraction grating by said interference fringes;
- and
- means for comparing phases of said first and second alternative outputs.
Dependencies are inferred from the claim text.