| 摘要 |
PURPOSE:To make it possible to detect a seam part regardless of the color, the presence or absence of a picture pattern and the quality of a material to be detected by detecting the fact that the transmitting amount of ultrasonic wave at the seam part of the material to be detected is decreased in comparison with the normal part in no contact with the material to be measured. CONSTITUTION:A squared wave A from an oscillating circuit 1 is amplified 2, and a square wave B is obtained. An ultrasonic wave is emitted from an ultrasonic transmitter 3 based on the square wave B. The most of the wave is reflected from the surface of a material to be detected 4, and the remaining part is transmitted through the material. A part of it is received with an ultrasonic wave receiver 5, and the other is reflected. The transmitted amount which is received with the receiver 5 is slightly reduced at a thick seam part than at a normal part. Then, the output of the receiver 5 is detected with a preamplifier 6, a detector circuit 7 and a low-pass filter circuit 8 in a detector part. A reference value is generated in a sensitivity adjuster 10 based on a peak value which is held with a peak hold circuit 9 in a discriminating part. The values are compared in a comparator circuit 11. Whether the detected value is larger or smaller than the reference value is discriminated, and the seam part is detected. |
