2000 年 66 巻 6 号 p. 960-964
In this study, the technology that detects the small cracks caused in a sodium lamp tube on a production line is developed. In particular, in this report, the detection principle and the experimental apparatus produced based on this principle are discussed. The crack is illuminated by a laser and the light scattered backward by the crack is collected by a Fresnel lens. The light intensity is converted into an electric signal by a photomultiplier tube. Experimental results indicate that cracks longer than 1.0 mm are detected automatically. This detection principle is analyzed theoretically using the Maxwell equation. It is verified experimentally and theoretically that the detection principle is effective for the detection of cracks in a sodium lamp tube.