| 摘要 |
PURPOSE:To surely detect an interface even when few specific gravity or impedance between upper and lower layers exists by receiving modulated light projected from the inside of a guide pipe on one side to that of a guide pipe on the other side, and detecting the interface by observing the output level of a light receiving means with a modulation light reception circuit. CONSTITUTION:A pair of guide pipes 22, 24 are provided with translucent property, and are arranged keeping a prescribed gap. Also, a modulation light driving circuit drives a light emitting means by outputting a modulation signal. The light receiving means receives the modulated light projected from the inside of the pipe 22 on one side to the pipe 24 on the other side via the pipes 22, 24 and an object to be inspected. The modulation light reception circuit detects the interface 8 with the interface detector 10 by observing the output level of the light receiving means. Therefore, since there is no influence on the transmittancy of the upper layer 4 and the lower layer 6 even when the specific gravity or the impedance of the upper layer 4 and the lower layer 6 is changed, the interface 8 can be surely detected. Similarly, when small difference in the specific gravity or impedance between the upper layer 4 and the lower layer 6 exists, the interface 8 can be detected. |
