An optical position measuring instrument including a scanning plate and a scale, wherein the scale and the scanning plate are movable relative to one another. The optical position measuring instrument including a grating and a light source that emits a beam toward the grating, wherein the grating receives the beam and splits the beam into two partial beams with orthogonal polarization states. The optical position measuring instrument including a polarizer being arranged in beam paths of the two partial beams, wherein the polarizer has a structure to generate polarization effects on the two partial beam striking the polarizer that are periodically variable, wherein a polarization period of the periodically variable polarization effects is greater than a graduation period of the grating. The two partial beams being reunified into a resultant beam. A detection unit that receives the resultant beam and generates a plurality of displacement-dependent scanning signals.