Patent ID: 7639366

Claim:
A position-measurement device for determining positions of two objects movable with respect to each other along a measurement direction, comprising: a first radiation source adapted to emit first electromagnetic beams of rays; a second radiation source adapted to emit second electromagnetic beams of rays a beam splitter adapted to split each beam of rays emitted by the radiation sources into at least one first partial beam of rays and one second partial beam of rays; a reference reflector arranged in a beam path of the first partial beam of rays; a measurement reflector movable with respect to the reference reflector along the measuring direction and arranged in a beam path of the second partial beam of rays; a superposition device adapted to superpose the first partial beam of rays and the second partial beams of rays after reflection of the first partial beam of rays by the reference reflector and after reflection of the second partial beam of rays by the measurement reflector; a combining device adapted to combine the second electromagnetic beams of rays into a beam path of the first electromagnetic beam of rays generated by the first radiation source; a detection device including a plurality of detectors, each detector adapted to receive the superposed first partial beam of rays and second partial beam of rays superposed by the superposition device, the detection device adapted to form a reference signal generated by superposition of the first electromagnetic beams of rays and the second electromagnetic beams of rays; and an evaluation device adapted to form a reference pulse as a function of a position of the reference reflector and the measurement reflector with respect to each other by evaluation of the reference signal.