Abstract: An improved solid state commutated linear motor with an ironless multiphase armature is disclosed which has a magnetic field array having periodic alternating polarity, an ironless multiphase armature, and a solid state commutating system for driving a moving element and positioning it with respect to a reference element. In one embodiment, the magnetic field array is elongated and fixedly located with respect to the reference element, and the ironless multiphase armature is fixedly located with respect to the moving element. In a second embodiment, the ironless multiphase armature is elongated and fixedly located with respect to the reference element, and the magnetic field array is fixedly located with respect to the moving element. The magnetic field array is generated by an array of spaced alternate north and south poled magnets having an inter-pole distance L.

Abstract: Statically pressurized gas bearings employ improved bearing pockets, each including one or more slots arranged in a double cross, star or other configuration, and supplemental gas exhaust slots, as well as stepped annular land flow restrictors, to optimize bearing stability and operational bandwidth.

Abstract: A dark field alignment system is provided wherein a bifurcated light source, including a secondary channel having spot sources of light located in a plane conjugate to the object plane of a reduction lens and directed through a peripheral ring of a plane conjugate to the apertgure plane of the reduction lens, illuminates the object plane of the reduction lens. Reflected and defracted light from an alignment mark of a semiconductive wafer in the image plane of the reduction lens is captured by a mirror located near the aperture plane of the reduction lens. This light is refocused to another plane conjugate to the object plane of the reduction lens and imaged onto detector arrays to provide alignment information.