Optical self-alignment system

摘要

An optical self-alignment system comprises a laser source, a substrate with a first diffraction grating for receiving laser beams from the laser source, a substrate with a second diffraction grating disposed within Fresnel zone of the first diffraction grating, and a photoelectric detector for detecting Fraunhofer diffraction ray of 0th order by the second diffraction grating. In order to adjust the relative position between the two substrates in orthogonal directions to the laser beams at high accuracy, the first and second diffraction gratings are provided with two groups of combined diffraction gratings so that phase difference of 180 DEG is produced in the Moire signals, maximum displacement point of Moire signal is detected with respect to relative position displacement of the diffraction gratings, and the substrates are positioned at maximum intensity displacement of two groups of the Moire signals.