Zone plate alignment aids on a mask and semiconductor wafer are used in a projection type system for aligning the wafer and mask prior to transfer of a circuit pattern from the mask to the wafer in an exposure process. The condenser system includes an aperture in the shape of a chevron or other convenient...http://www.google.ca/patents/US4545683?utm_source=gb-gplus-sharePatent US4545683 - Wafer alignment device
