| 摘要 |
PURPOSE:To surely detect the breakage of a drill having a small diameter by preventing the light reflected on the surface of a rear article from being transmitted into a light receiving fiber by installing a light absorbing body at the back of the drill and allowing the top edge of the drill to be reflected by the reflection type optical fiber. CONSTITUTION:When a slider 5 is positioned at a top dead center, the light reflected from the inlet/outlet edge 9 of a reflection type optical fiber 8 is transmitted towards the top edge part of a drill 1, and contacts the top edge part and is diffusion-reflected, and a portion of the light passes through a light receiving fiber 8b from the inlet/outlet edge 9, and detected by a light receiving element, and it is judged that no bending is generated at the top edge part. When the top edge part is broken, the light transmitted from the inlet/outlet edge 9 contacts the top edge of the drill 1, and passes free from the diffusion reflection, and inputted into a light absorbing body 11, and at least 90% is absorbed, and the light is not input into the reflection type optical fiber 8. Because the light receiving element does not detect light, the top edge of the drill 1 is judged to be broken. |
