Moire interferometric focusing system for optical microlithography.
An interferometric apparatus for detecting axial and angular misalignments of the film plane in a photolithographic camera is proposed. The misalignments are observed as moire interference fringes created by the superposition of a reference interferometric fringe pattern representing the focused camera and a perturbed fringe pattern produced when the camera is misfocused. The theory and results of a simple experimental implementation are described.
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