Patent ID: 6429940
Filing Date: 2002-08-06
Classification: G01D

Abstract:
An optical position measuring system, comprising:a scale comprising at least two partial measuring graduations that have different graduation periods, wherein said at least two partial measuring graduations comprise a first partial measuring graduation with a coarse graduation period and a second partial graduation period with a fine graduation period; a scanning unit that is movable relative to said scale along a measuring direction, said scanning unit comprising: a light source that emits light beams; a reflector element; and a detector element, wherein the light beams emitted by the light source are deflected several times by the reflector element in the direction of the course of propagation of the emitted light beams and impinge several times on said scale before they impinge on said detector element, on which scanning signals, which are modulated as a function of displacement, are detected; and wherein said light beams emitted by the light source initially impinge on the first partial measuring graduation, the impinging light beams are diffracted a first time and deflected in a direction toward said reflector element, said deflected light beams are again deflected by said reflector element in a direction toward said second partial measuring graduation, where light beams impinging on said second partial measuring graduation are diffracted a second time and deflected in a direction so as to impinge on said reflector element, which again said reflector element deflects said impinging light beams in a direction toward said first partial measuring graduation, where said first partial measuring graduation diffracts impinging light beams for a third time and said three time diffracted light beams are deflected in a direction toward said detector element.