Optical position-measuring device for suppressing disturbing higher diffraction orders

Abstract

An optical position-measuring device for determining a relative position of scales includes a light source, the scales and a detector. The scales are movable relative to each other along measurement directions and disposed in different planes in crossed relation to each other, and each have a graduation having grating regions which are arranged periodically and have different optical properties. At the first scale, the illumination beam is split into sub-beams, the sub-beams subsequently impinge on the second scale and are reflected back toward the first scale, and the reflected-back sub-beams strike the first scale again, where they are recombined, so that a resulting signal beam subsequently propagates toward the detector. The measuring graduation of one or more of the scales is configured as a two-dimensional cross grating which has a filtering effect that suppresses disturbing higher diffraction orders.