| 摘要 |
PURPOSE:To ensure the checking of the finished state of the inner surface simply by irradiating light on the concrete tube, photographing the part by a sensor, and comparing the change in the detected value due to the change in brightness with a reference value. CONSTITUTION:The light is irradiated from a light projecting device 4 on the inner surface 3a through a light screening plate 5 from the front side of the concrete tube A. The irradiated plate 5 from the front side of the concrete tube A. The irradiated part is photographed by the image sensor 6 from the rear side. The output is inputted to a comparator 10 through a low pass filter 7, a differentiating circuit 8, and a low pass filter 9, and compared with the reference value. When the output from the filter 9 exceeds the reference value, it is judged that the disturbance brightness is present on the inner surface 3a of the tube A due to the poor part wherein concave and convex parts exceed the specified value. The signal is sent to a warning circuit 11. Therefore the check of the finished state of the inner surface can be performed simply and accurately. |
