| 摘要 |
PURPOSE:To accurately detect a defect in a filament, by a method wherein a single light source is arranged as opposed to a light receiving unit to form an optical path and a filament runs through a filament path intercepting the optical path to detect changes in balance with a difference generated between outputs of two solar cells. CONSTITUTION:Optical paths between solar cells and a light source serve as paths of a filament 2. For example, when a normal filament passes, the interception level of the optical path is the same between the solar cells (A) and A' and hence, there is no difference in the electromotive force between the solar cells. But when a defect or the like passes through the optical path, there is a difference generated in the electromotive force between the solar cells (A) and (A'). With such an arrangement, an output difference between solar cells as generated when a defect of a filament passes through a crossing area is detected to make a relay circuit respond. In this case, only when an output difference is generated in the either of optical paths in crossing two directions, the relay circuit is made to respond thereby eliminating malfuctioning. |
