Patent ID: 8351049

Claim:
An interferometric device for position measurement of an element moveable in a plane, comprising: a laser light source for supplying measuring light required for position measurement; one first beam splitter for splitting the measuring light into a first partial beam path and a second partial beam path; a second beam splitter provided in the first beam path for directing a third partial beam path onto an etalon for reference measurement via an interferometer; one or more third beam splitters each positioned in one of the first partial beam path and the second partial beam path, so that the one of the first partial beam path and the second partial beam path impinge on reflecting surfaces of the moveable element via a respective interferometer; and a respective beam trap associated with each of the first beam splitter, the second beam splitter and the third beam splitter, each beam trap trapping light returned by one of the interferometers, wherein the one or more third beam splitters includes a plurality of third beam splitters formed as 50/50 splitters.