Patent ID: 9141003
Filing Date: 2015-09-22
Classification: G01B,G03F

Abstract:
1. A position measurement system configured to measure a position quantity of a movable object in a measurement direction, the position measurement system comprising: a radiation source configured to emit a single radiation beam; a beam splitter configured to split the single radiation beam into a measurement beam and a reference beam; a first reflective surface mounted on the movable object and configured to receive the measurement beam; a second reflective surface mounted on a reference object and configured to receive the reference beam; and a detector arranged to receive a first reflected beam reflected by the first reflective surface and a second reflected beam reflected by the second reflective surface, the detector configured to provide a signal representative of the position quantity of the movable object on the basis of the first and the second reflected beam, wherein the radiation source and the detector are mounted on another object that is different from the movable object and the reference object, and wherein the other object is a balance mass of a stage system.