Stage-position measuring apparatus

Claim 2

A position measuring apparatus for detecting a position of a stage movable in a predetermined direction on a base, comprising: a movable mirror having a reflecting surface perpendicular to the direction of movement of said stage and mounted on a portion of said stage; a fixed mirror disposed fixedly relative to said base; a light wave interferometer projecting coherent light beams substantially perpendicularly to respective ones of said movable mirror and said fixed mirror, causing the light beams reflected by respective ones of said movable mirror and said fixed mirror to interfere with each other and receiving said light beams, and photoelectrically detecting said interference beams and outputting a measurement signal; a position detecting circuit for detecting the position of said stage based on said measurement signal; first cover means covering a beam optical path from said light wave interferometer to said fixed mirror; second cover means covering a beam optical path from said light wave interferometer to said movable mirror, said second cover means having its dimension in the direction of said beam optical path variable with the movement of said stage; and gas supply means for supplying gas of controlled temperature to interiors of said first cover means and said second cover means at a predetermined flow rate.

Claim 3

A position measuring apparatus according to claim 1, wherein said first cover means is a tube through which said light beam passes and which has a length substantially equal to the length of the optical path of said light beam, said tube having a first end portion located on said interferometer side and a second end portion proximate to said fixed mirror, said first end portion having a minute opening through which said light beam passes, said second end portion having a large opening, and said gas supply means communicates with said tube near said first end portion, whereby said gas supply means flows said gas of controlled temperature outwardly through said large opening.

Claim 4

A position measuring apparatus for detecting a position of a stage movable in a predetermined direction on a base, comprising: a movable mirror having a reflecting surface perpendicular to the direction of movement of said stage and mounted on a portion of said stage; a fixed mirror disposed fixedly relative to said base; a light wave interferometer projecting coherent light beams substantially perpendicularly to respective ones of said movable mirror and said fixed mirror, causing the light beams reflected by respective ones of said movable mirror and said fixed mirror to interfere with each other and receiving the reflected light beams, and photoelectrically detecting said interference beams and outputting a measurement signal; a position detecting circuit for detecting the position of said stage based on said measurement signal; cover means covering a beam optical path from said light wave interferometer to said fixed mirror, said cover means being invariable in its dimension in the direction of said beam optical path; and gas supply means for supplying gas of controlled temperature to an interior of said cover means at a predetermined flow rate.

Claim 5

A position measuring apparatus for detecting a position of a stage movable in a predetermined direction on a base, comprising: a movable mirror having a reflecting surface perpendicular to the direction of movement of said stage and mounted on a portion of said stage; a fixed mirror disposed fixedly relative to said base; a light wave interferometer projecting coherent light beams substantially perpendicularly to respective ones of said movable mirror and said fixed mirror, causing the light beams reflected by respective ones of said movable mirror and said fixed mirror to interfere with each other and receiving the reflected light beams, and photoelectrically detecting said interference beams and outputting a measurement signal; a position detecting circuit for detecting the position of said stage based on said measurement signal; cover means covering a beam optical path from said light wave interferometer to said fixed mirror, said cover means being invariable in its dimension in the direction of said beam optical path; and gas supply means for supplying gas of controlled temperature to an interior of said cover means at a predetermined flow rate.

Claim 6

A position measuring apparatus according to claim 3, wherein said cover means is a tube through which said light beams pass and which has a length substantially equal to a length of the optical path of said light beams, said tube having a first end portion located on said interferometer side and a second end portion proximate to said fixed mirror, said first end portion having a minute opening through which said light beams pass, said second end portion having a large opening, and said gas supply means communicates with said tube near said first end portion, whereby said gas supply means flows said gas of controlled temperature outwardly through said large opening.

Claim 7

A position measuring apparatus according to claim 4, wherein the light beam travelling toward said fixed mirror and the light beam travelling toward said movable mirror are applied in parallelism, the side of said tube has a plurality of minute holes formed along the light beam travelling toward said movable mirror, and part of said gas of controlled temperature supplied into said tube is supplied substantially perpendicularly to the light beam travelling toward said movable mirror through said minute holes.

Claim 8

A position measuring apparatus for detecting a position of a stage movable in a predetermined direction on a base, comprising: a movable mirror having a reflecting surface perpendicular to the direction of movement of said stage and mounted on a portion of said stage; a fixed mirror disposed fixedly relative to said base; a light wave interferometer projecting coherent light beams substantially perpendicularly to respective ones of said movable mirror and said fixed mirror, causing the light beams reflected by respective ones of said movable mirror and said fixed mirror to interfere with each other and receiving the reflected light beams, and photoelectrically detecting the interference beams and outputting a measurement signal; a position detecting circuit for detecting the position of said stage based on said measurement signal; first cover means covering a beam optical path from said light wave interferometer to said fixed mirror; second cover means covering a part of a beam optical path from said light wave interferometer to said movable mirror which is near said movable mirror; and gas supply means for supplying gas of controlled temperature to interiors of said first cover means and said second cover means at a predetermined flow rate, and flowing said gas of controlled temperature within said second cover means from said movable mirror toward said light wave interferometer.

Claim 9

A position measuring apparatus for detecting a position of a stage movable in a predetermined direction on a base, comprising: a movable mirror having a reflecting surface perpendicular to the direction of movement of said stage and mounted on a portion of said stage; a fixed mirror disposed fixedly relative to said base; a light wave interferometer projecting coherent light beams substantially perpendicularly to respective ones of said movable mirror and said fixed mirror, causing the light beams reflected by respective ones of said movable mirror and said fixed mirror to interfere with each other and receiving the reflected light beams, and photoelectrically detecting the interference beams and outputting a measurement signal; a position detecting circuit for detecting the position of said stage based on said measurement signal; first cover means covering a beam optical path from said light wave interferometer to said fixed mirror; second cover means covering a part of a beam optical path from said light wave interferometer to said movable mirror which is near said movable mirror; and gas supply means for supplying gas of controlled temperature to interiors of said first cover means and said second cover means at a predetermined flow rate, and flowing said gas of controlled temperature within said second cover means from said movable mirror toward said light wave interferometer.

Claim 10

A position measuring apparatus according to claim 6, further comprising means for moving said second cover means with said stage when said stage is moved in the direction of said beam optical path, and stopping said second cover means relative to said beam optical path when said stage is moved in a direction orthogonal to the direction of said beam optical path.