Patent ID: 9043182
Filing Date: 2015-05-26
Classification: G01B

Abstract:
1. An interferometer for measuring an absolute position of an object based on an origin point, the interferometer comprising: a first light source; a second light source which has coherency lower than that of the first light source; and a signal processing unit programmed and configured (a) to obtain (1) a first point where a phase of an interference signal obtained from the first light source coincides with a phase of an interference signal obtained from the second light source and (2) a second point where an intensity of the interference signal obtained from the second light source is maximized; (b) to define the origin point based on the obtained first and second points; (c) to store a phase of the interference signal obtained from the first light source at the defined origin point; and (d) to redefine, if information of the origin point is cleared, the origin point based on (1) the first and second points having been reobtained and (2) a third point where the interference signal obtained from the first light source has the stored phase.