Patent ID: 7966158
Filing Date: 2011-06-21
Classification: G01D

Abstract:
1. A measurement apparatus configured to measure a position of an object using a plurality of different phase signals obtained based on displacement of the object, the apparatus comprising: a distortion correcting unit configured to generate a plurality of correction signals by correcting the corresponding plurality of different phase signals using a corresponding distortion coefficient which is stored in the apparatus; a square-root of sum of squares arithmetic unit configured to calculate a square-root of sum of squares of the plurality of correction signals; a first normalizing unit configured to generate a plurality of first normalized signals by dividing the corresponding plurality of correction signals by the square-root of sum of squares; a phase arithmetic unit configured to calculate a phase corresponding to the position of the object based on the plurality of first normalized signals; an averaging arithmetic unit configured to average a plurality of the square-root of sum of squares over one cycle of the plurality of correction signals; a second normalizing unit configured to generate a plurality of second normalized signals by dividing the corresponding plurality of correction signals by the averaged square-root of sum of squares; and