摘要：

Optical system for the automatic alignment of two motifs in which the alignment marks of a first fixed motif forming the reference are constituted by at least one pair of identical periodic optical gratings with a constant spacing P and having a predetermined distance d. sub.X from one another such that the equation d.sub.X =(n+&egr;) P is proved, n being an integer and &egr; a fraction of unity.< P>An optical modulator, for example electro-optical means incorporating a Pockels cell alternately illuminate with the timing of the high frequency control signals, the said gratings in windows, whose position can be regulated in accordance with a given axis. The image of these windows is projected onto gratings carried on a second moving support to be aligned and produces orders of diffraction. An optoelectronic detector detects a predetermined order of diffraction. The high frequency- modulated output signals are transmitted to control circuits for producing the automatic alignment.

展开