Abstract: A master disk is positioned such that a radial portion thereof is within a restricted field having good imagery of an optical projection system. A second blank disk is positioned such that the image location extends along a radial portion thereof. As the two disks are rotated synchronously a pattern in an annular area is formed on the blank disk replicating the master. Good imagery of the pattern is obtained with a simple system having an image field less than the size of the object being reproduced.

Abstract: An apparatus for aligning a wafer. The edge of a wafer is mapped by means of a photodetector array and a light source to provide a signal representative of the X-Y position and angular orientation of the wafer as the wafer is rotated one revolution on a shaft. The signal is digitized and processed to provide stored information of the X-Y position and angular orientation of the wafer. The shaft is then rotated to move the wafer from its calculated angular orientation to a desired angular orientation. The X-Y positional information may be used to center the wafer.

Abstract: A unity magnification catoptric image-forming system and an illumination system on the one hand, and an object- and image-surface supporting means on the other hand, are arranged for relative movement to retain the object and image surfaces in unity magnification conjugate planes of the catoptric system while effecting a scanning-type exposure of successive portions of the image surface to successively illuminated portions of the object. Fine motion mechanisms permit accurate preliminary adjustment of the object- and image-receiving surfaces relative to each other while under visual examination with the aid of the catoptric image-forming system.

Abstract: A viewing system for an annular projection system, particularly useful to provide a view of a semiconductor wafer on which an image of a integrated circuit mask pattern has been projected using an annular field projection system in which the field of view can be as large as the large dimension of that portion of the annular region subtended by the wafer thereby permitting ideal coarse alignment of the mask and wafer. The system further includes means to illuminate the mask and wafer separately and in different colors to thereby simplify the distinction of one from the other in the combined image thus facilitating the alignment task.