Abstract: An optical device projects a pattern of a first object on a second object through an optical system. Changes in the temperature of the optical system or changes in the ambient temperature of the optical system are detected and, on the basis of the detected temperature, any focus deviation or displacement of the optical system due to the temperature change is corrected. The correction of the focus deviation is achieved by controlling the temperature of the optical system or the position of the second object.

Abstract: An apparatus for aligning objects on the basis of a signal obtained by scanning marks formed on the objects. A position datum representing the relative position between the objects is extracted on the basis of an extraction level. The marks are scanned a plurality of times and an average is obtained by the plural data provided on the basis of the extraction datum. Those operations are repeated with one or more different extraction levels. In each of the data group corresponding to one of the extraction data, a peculiar or exceptional datum is determined. Among the peculiar data obtained for individual sets of data, a minimum is selected. Thus, an extraction datum which results in the minimum peculiar datum is determined. The average of the position data obtained with this extraction datum is used for bringing the objects into alignment with each other.

Abstract: A wafer pre-alignment apparatus including a mechanical pre-alignment device for positioning a wafer on the basis of an outer periphery configuration of the wafer, an image processing pre-alignment device for positioning the wafer on the basis of a pattern of an image formed on the wafer the image processing aligner being effective to perform the pre-alignment operation with a higher accuracy than the mechanical aligner, and a selector for operating the apparatus selectively in a first mode wherein the mechanical aligner only is operated for the wafer and in a second mode wherein the image processing aligner only is operated for the wafer, or the mechanical aligner and the image processing aligner are operated sequentially for the wafer.

Abstract: An alignment apparatus for positioning on a wafer an image of a mask formed by a projection optical system. The apparatus includes a first detecting system for detecting the distance between an imaging plane of the optical system and the wafer, a driving mechanism for moving the wafer in the direction of the optical axis of the optical system and a second detecting system for detecting the amount of movement of the wafer. The driving mechanism is controlled while the distance detected by the first detecting system is compared with the amount of movement detected by the second detecting system, whereby the wafer is correctly and accurately positioned on the imaging plane of the optical system.

Abstract: Disclosed is a transfer apparatus provided with a first body having a plurality of alignment marks, a second body having a plurality of alignment marks, a projection optical system for projecting the image of the first body upon the second body, a probing device for probing the alignment marks of the first body and probing the alignment marks of the second body through the projection optical system, an operation device electrically coupled to the probing device and deriving a transfer error from the alignment error of the alignment marks, and a compensation device coupled to the operation device for eliminating the transfer error and for compensating for the projection optical system.