Reticle transporter

Claim 1

Apparatus for precisely and rapidly transporting a reticle past an optical slit which comprises: a base member having thereon a first planar bearing surface and a second planar bearing surface, said first and second bearing surfaces lying in intersecting planes whereby they are angularly disposed relative to each other; a reticle stage linearly movable along the line of intersection of said planes; three triangularly disposed gas bearings mounted on said reticle stage for supporting it on each of said first and second bearing surfaces, each of said gas bearings having planar supporting surface movable along one of said first and second bearing surfaces, said supporting surface defining a vacuum chamber and a plurality of pressure chambers adjacent its respective bearing surface; means for simultaneously connecting said vacuum chamber to a vacuum source and said pressure chamber to a pressurized gas source whereby pressurized gas permits essentially friction-free movement of said reticle stage along said bearing surfaces while vacuum prevents movement of said reticle stage away from said bearing surfaces; and means for propelling said reticle stage along said bearing surfaces.