Patent ID: 8949071
Filing Date: 2015-02-03
Classification: G01B

Abstract:
1. A circularity measuring apparatus for measuring a circularity of a substantially circular measurement target by mounting the measurement target on a mount base in a manner that a center of the measurement target matches with a center of rotation and rotating the measurement target relative to a detector, the apparatus comprising: a driving device which linearly moves the detector relative to a measurement target mounted on the mounting base; a center deviation amount calculating device which, when the driving device linearly moves the detector relative to a substantially circular reference measurement target with a known diameter mounted on the mounting base and the detector measures a distance between two detection points which are two points on a path along which the detector moves and on a perimeter of the reference measurement target, calculates a center deviation amount representing a distance between the center of the reference measurement target and a straight line representing the path along which the detector moves based on the diameter of the reference measurement target and the distance between the two detection points; and a measurement value correcting device which, when the driving device linearly moves the detector relative to an arbitrary measurement target mounted on the mounting base instead of the reference measurement target and the detector measures as a diameter of the arbitrary measurement target, a distance between two detection points which are two points on the path along which the detector moves and on a perimeter of the arbitrary measurement target, corrects the diameter of the arbitrary measurement target using the center deviation amount.