ALIGNMENT PROCESS AND DEVICE THEREOF

摘要

PURPOSE:To perform the alignment of two members with diffractive grids with high precision by a method wherein two wavelength beams with slightly different frequency are entered into two diffractive grids arranged in parallel with each other to transmit the diffractive beams only exceeding one time diffraction. CONSTITUTION:Two kinds of beams with slightly different frequency emitted from a two wavelength orthogonal polarized laser beam source 33 passing through a beam splitter 21 and a condenser are inputted in a photodetector 25 to be transmitted to a signal processor 26 as reference beat signals. Besides, said beams are divided into two wavelength beams with slighly different frequency to be entered into a transmitted diffractive grid 29 and a reflected diffractive grid 30 at specified incident angle. Finally the diffractive beams from the grids 29, 30 are detected by a photodetector 25' to be transmitted to the signal processor 26 as diffractive beam beat signals. Through these procedures, the position slips can be detected referring to the phase difference from the reference beat signals.