Patent ID: 7710578

Claim:
A position measuring arrangement for detecting a relative position of a scanning unit and a reflection scale graduation which is moved in relation to said scanning unit in a measuring direction, the position measuring arrangement comprising: a reflection scale graduation; and a scanning unit comprising a plurality of optical elements, said plurality of optical elements comprising; a combining grating; a retro-reflector element; a scanning grating; and a plurality of detector elements, wherein said plurality of optical elements are arranged so that: light beams and/or partial light beams of a scanning beam path act on said reflection scale graduation at least twice, and in the course of this a plane is defined on the one hand by incident light beams and/or partial light beams that impinge on said reflection scale graduation, and on the other hand by reflected partial light beams that reflect off of said reflection scale graduation, wherein said plane is oriented perpendicularly to a graduation plane defined by said reflection scale graduation, a directional reversal of said incident partial light beams impinging on said reflection scale graduation perpendicularly with respect to said measuring direction takes place by said retro-reflector element; and a pair of partial light beams impinges in a non-parallel manner on said combining grating, and said combining grating brings said partial light beams impinging on said combining grating to interference, so that phase-shifted signals are detected by said plurality of detector elements.