Abstract: X-Y position measurement apparatus is employed with feedback controlled X-Y positioning apparatus for positioning a workpiece stage at a desired X-Y coordinate position in response to signals indicative of the actual position and the desired position of the workpiece stage. A normalization circuit is employed for gain correction of the signals indicative of the actual position of the workpiece stage.

Abstract: A projection lens and a source of illumination and exposure light are employed for projecting an image of a reticle onto a first reference mark or a semiconductive wafer, both of which are movably supported in the image plane of the projection lens. Optical apparatus, including an objective lens unit and an imaging lens, is provided for imaging light from the source of illumination and exposure light at the reticle and for reimaging reflected light from the semiconductive wafer at the objective lens unit. Additional optical apparatus, including a source of nonexposure light, is provided and is operable with the projection lens for imaging a second adjustable reference mark onto the first reference mark or the semiconductive wafer to facilitate use of the projection lens in aligning a semiconductive wafer covered with a photoresist opaque to exposure light.

Abstract: A projection lens and a source of exposure light are employed for projecting an image of a reticle onto a first reference mark or a semiconductive wafer, both of which are movably supported in the image plane of the projection lens. Optical apparatus, including a source of nonexposure light and the projection lens, is provided for imaging a second adjustable reference mark onto the first reference mark or the semiconductive wafer to facilitate use of the projection lens in aligning a semiconductive wafer covered with a photoresist opaque to exposure light.