| 摘要 |
PURPOSE:To efficiently detect the cracking between two areas, by dividing beam into two detection beams to irradiate areas separated by an arbitrary distance with said detection beams to obtain the interference image of the reflected beams thereof and detecting the timewise change in an interference pattern. CONSTITUTION:Coherent beam is emitted from a laser 1 and split into two beams by a beam splitter 2 while the two beams are allowed to irradiate two points A, B separated by an arbitrary distance on the surface of an object 3 to be detected. The reflected beams from two points A, B are incident to an image sensor 6 by an image forming optical system 4 and a mirror 5 to form an image thereon and an interference image is obtained. Then, the object 3 is vibrated and, when there is cracking between two points A, B, the phases of the vibration waves of both points A, B are shifted and the interference pattern on the image sensor 6 varies timewise. Because the timewise change of the interference pattern is detected, cracking can be detected with high reliability. |
