Patent ID: 7207720

Claim:
An apparatus comprising: a static gas bearing provided upon a first object and configured to form a gas layer between the first object and a second object by use of gas supplied thereto, and to support the first object movably relative to the second object; a plurality of exhaust grooves provided upon the first object and configured to surround said static gas bearing; and a plurality of exhaust flowpassages provided through the first object, connecting to a respective one of said plurality of exhaust grooves, and configured to exhaust gas from a respective one of said plurality of exhaust grooves, wherein an outermost exhaust flowpassage of said plurality of exhaust flowpassages connected to an outermost exhaust groove, which is an outermost one of said plurality of exhaust grooves with respect to said static gas bearing, is shorter than an innermost exhaust flowpassage of said plurality of exhaust flowpassages connected to an innermost exhaust groove, which is an innermost one of said plurality of exhaust grooves with respect to said static gas bearing, so that a conductance of said outermost exhaust flowpassage is greater than that of said innermost exhaust flowpassage.