| 摘要 |
Subtle deformations of metal elements (13) can be reliably detected because deformation of the metal elements (13) is detected by: configuring a metal element row (13') wherein multiple metal elements (13) are in line contact with each other at rocking edges (21) to form an arc-shaped line; disposing a light source (33) on the inside or the outside of the arc of the metal element row (13') in the radial direction; and observing light passing from the light source (33) through gaps between adjacent metal elements (13). When observing light passing through gaps formed between portions that are in surface contact, there are cases in which, depending on the angle of observation, the permeating light is blocked and observation is not possible. But observing light passing through gaps formed at a rocking edge (21), which is in line contact with the adjacent metal element (13), makes blockage of said permeating light less likely and improves detection accuracy. |
