Patent ID: 7030518

Claim:
A position-control stage comprising a bed, a turntable supported for rotation on the bed through a rolling-contact bearing, a linear motor moving the turntable relatively to the bed in a circular direction, and an encoder monitoring a relative position of the turntable to the bed; wherein the linear motor is comprised of armature windings at a primary side and field magnets at a secondary side; wherein the armature windings are each made of a three-phase coreless coil where winding turns are wound in a form of flat rectangular loop, are circularly arranged on a disc surface of the bed along a preselected curvature, and lie in radial juxtaposition in circumferential direction; wherein the field magnets are made in a flat shape and arranged underneath the turntable in such a pattern lying radially on a disc surface of the preselected curvature in opposition to the armature windings, with their unlike poles alternating in polarity along a circular direction; wherein the linear motor in minimum unit is comprised of three armature windings and five field magnets; and wherein the field magnets are disposed on the disc surface of the turntable throughout an overall circular direction while the armature windings lie on the disc surface of the bed over a preselected area in the circular direction in case where the position-control stage requires large circular angle in relative turning of the turntable to the bed.