| 摘要 |
PURPOSE:To detect a defect with high sensitivity by irradiating a scan laser beam to a cylindrical light-permeable substance such as glass tube, etc. and detecting a concurrent increase in the output of at least two pieces of a scattering diffracted light receiving part and a decrease in the output of a transmitting light receiving part. CONSTITUTION:A laser beam from a laser source 2 is reflected on a rotary oscillation mirror 3 and is collimated by means of a lens 4, scanning and being irradiated to a body to be detected 1 such as glass tube, etc. A condensing lens 5 is arranged at the opposite side to the lens 4 and a permeating light receiving part 6 is installed at a focusing position on the opposite side to the body to be detected 1 for the lens 5. In addition, a pair of light receiving parts 7, 8 for reception of scattering diffracted light through the lens 5 are arranged at a symmetrical position against a line connecting the center of the body to be detected 1 and the light receiving part 6. In the same manner, a pair of light receiving parts 11, 12 for scattering diffracted light reception through condensing lens 9, 10 are provided. Each light receiving part 6 to 8, 11, 12 converts a change in the receiving light value to a change in voltage. The output of at least two pieces of the light receiving parts 7, 8, 11, 12 is synchronized and increased in a detection circuit 13. In addition, the said circuit 13 outputs a defect signal to a display part 14, detecting a reduced output from the light receiving part 6. |
