INTERFEROMETRISCHE MASKENSUBSTRATAUSRICHTUNG.

摘要

Two optical gratings in conjugate planes of an imaging system are aligned by illuminating one grating (3a) with a laser beam (2) so that the first symmetrical diffraction orders are selected and focused by an imaging system (7) to coincide on a second grating (8a) to be further diffracted thus obtaining second diffraction orders. The phase relationship between the diffracted beams is modulated periodically because the pattern from the second grating is colinear to the optical axis of the imaging system. The relative phase of the second diffraction orders is evaluated. The gratings are linear and parallel to each other alignment in a direction perpendicular of the grating bars.