Inner Circumferential Length Measurement Method for Circular Member

Abstract

An inner circumferential length measurement method includes the steps of: disposing a two-dimensional sensor at a predetermined measurement position on an inner side of the circular member placed flat in an unrestrained state on a support so that the two-dimensional sensor faces an inner circumferential surface of the circular member in a non-contact state; rotating the two-dimensional sensor about rotation shaft at a predetermined position on the inner side of the circular member; measuring a separation distance from the two-dimensional sensor to the inner circumferential surface around an entire circumference of the circular member; and calculating an inner circumferential length of the circular member via a calculation unit using the separation distance measured and a distance from the rotation shaft to the two-dimensional sensor in a plan view.

Dependencies are inferred from the claim text.