Optoelectronic projection-type inspection system insensitive to displacements and rotation of an object

A method was developed for obtaining a negative image in an optoelectronic projection system for the examination of features of an object. The method was based on a phase shift, by π, of the zeroth-order diffraction maximum in a confocal configuration of the mirrors ensuring insensitivity of the analyzed Fourier transform to displacements of a dark-field object. Experiments were made in which two objects were identified in the case of arbitrary displacement and rotation of the objects when a sector–ring detector was employed. The advantages of using such a configuration in inspection systems were identified.