Patent ID: 8665455
Filing Date: 2014-03-04
Classification: G01D,G03F

Abstract:
1. A movable body apparatus including a movable body which substantially moves along a predetermined plane, the apparatus comprising: a scale which is arranged at one of the movable body and an outside of the movable body, with a first direction within a plane parallel to the predetermined plane serving as a longitudinal direction, the scale having a grating section that has a predetermined width in a second direction orthogonal to the first direction within the plane parallel to the predetermined plane; a measurement device which has a plurality of measurement points placed in a movement area of the movable body, and measures positional information of the scale in a periodic direction of the grating section by irradiating measurement beams on the measurement points placed on the scale within the predetermined width; and a controller which performs position control of the movable body, preferentially using a first measurement information including measurement information at a first measurement point out of n (wherein n is an integer of two or more) or more measurement points positioned within the predetermined width of the scale, and which switches measurement information to preferentially use in position control of the movable body to a second measurement information including measurement information at a second measurement point different from the first measurement point when abnormality occurs in the first measurement information at the first measurement point, wherein the controller determines whether the abnormality has occurred by comparing the first measurement information with a predicted measurement value.