Method for the testing of optical systems using moiré fringes

摘要

A method for testing optical imaging systems by the use of moire stripes, wherein two copies of an optical grating are made and simultaneously illuminated to produce a moire pattern which is a measure of the distortion of the imaging system. In a first step an original grating is transferred by a light beam as a contact copy onto a substrate. In a second step, the imaging system to be tested copies the original grating for a second time onto the substrate, except that the second grating copy is rotated slightly with respect to the first grating copy. The points of intersection of the two superimposed gratings produce moire stripes when illuminated, the positions of the stripes being calculated precisely with the assumption that ideal gratings were used. If the imaging system to be tested shows distortions, the position of the moire stripes that are observed will not correspond to these calculated positions. The deviation therefrom is a measure of the imaging system errors.