Form measuring apparatus and method of registering coordinate system for rotary table

摘要

A form measuring apparatus includes a probe for measuring a measured object; a rotary table on which the measured object is placed; and a coordinate system calculator calculating coordinate axes configuring a coordinate system for the rotary table. The coordinate system calculator calculates, based on a position of a master ball fixed to the rotary table, a center of a circle traced by the master ball when the rotary table is rotated; calculates a rotary table coordinate system having the center of the circle as an origin point; and corrects coordinates of the origin point based on a calibrated diameter value of a gauge fixed to the rotary table, a first diameter value of the gauge measured by a first measurement in which the probe approaches the gauge in a first direction, and a second diameter value of the gauge measured by a second measurement.