| 摘要 |
PURPOSE:To detect a flaw in a clear image regardless of a width or a length of the flaw by arranging an adding and subtracting part which adds image signals successively and subtracts the image signals added before the prescribed number of times. CONSTITUTION:Inspection light is inspected in the width direction to the surface of a moving steel plate 5, and transmitted light is received by a light receiving unit 4. An image storage device 7 stores an image signal which is outputted from the light receiving unit 4 and is generated by light leaked from a pin hole of the steel plate 5. An adding and subtracting circuit 8 adds image signals inputted from the light receiving unit 4 with respective width directional positions every time the steel plate 5 advances by the scanning pitch. At the same time, it subtracts the oldest data, that is, scanning image signals of before the prescribed number of times among image signals inputted from the storage device 7 with respective width directional positions. Addition and subtraction data obtained in this way becomes an integration value with respective width directional positions within the newest integral range. Moreover, this data is renewed every time the steel plate 5 advances by the scanning pitch, so that even a microscopic flaw 6 can be detected. |
