Patent ID: 7112782

Claim:
An optical position measuring system, comprising: a scale comprising a scale graduation with scale graduation marks, which are periodically arranged at a scale graduation period, TP M , in a measuring direction; a scanning unit, which is movable with respect to said scale in at least said measuring direction, said scanning unit comprising: a light source that emits light beams; a periodic scanning graduation comprising scanning graduation marks arranged periodically at a scanning graduation period along said measuring direction, wherein said scale graduation period, TP M , and said scanning graduation period differ from each other; and a detector arrangement, by which in case of a relative movement between said scale and said scanning unit at least one periodic scanning signal is detected, which results from scanning a periodic Vernier fringe pattern having a fringe pattern period in a detector plane of said detector arrangement; wherein said scale graduation comprises at least three partial tracks, which adjoin perpendicularly with respect to said measuring direction, and graduation marks associated with each of said at least three partial tracks have a defined and constant offset spacing from their nominal positions, wherein said offset spacings associated with adjoining ones of said at least three partial tracks differ, so that filtering of undesired harmonic waves out of said at least one periodic scanning signal results from said offset spacings.