| 摘要 |
PURPOSE:To prevent omission of detection and erroneous detection and to perform highly reliable detection by providing a reflection mirror on the path of transmitted light that passes through a punch hole and picking up the reflected light by an image sensor camera. CONSTITUTION:Light is projected by a light projector 1 from one side of a running steel plate P. A reflection mirror 4 slanting, for instance, 45 deg. is provided on the path of transmitted light that passed a punch hole H, and an image sensor camera 3 is placed on the path of reflected light. By this way, the round shape of the punch hole H can be picked up as it is even when the image sensor camera 3 for which space of installation is limited is not right above the light projector 1, and the omission of detection or the erroneous detection can be eliminated surely. |
