OPTICAL ALIGNING SYSTEM FOR TWO PATTERNS AND PHOTOREPEATER MAKING USE OF SUCH A SYSTEM

摘要

An optical system for aligning two patterns particularly by photo-repetition in which a first pattern formed by two optical networks, disposed along two coordinate axes is illuminated by the image of a second pattern comprising two optical networks, forming a reference produced from the orders of diffraction. In a variation, the optical networks are formed from a series of parallel strokes whose thickness and spatial distribution in a first direction parallel to one of the coordinate axes are determined by a pseudo-random code; the strokes of the optical networks of the first pattern being furthermore interrupted periodically in a second direction orthogonal to the first direction so as to form an optical network with a constant pitch in this direction. The optical alignment system comprises means for detecting the intensity of a predetermined part of the orders of diffraction in the second direction.