| 摘要 |
PURPOSE:To enable excited ultrasonic waves to be correctly, surely and efficiently measured in a completely noncontact state even if the surface of material is rough by generating a scanning interference fringe by double channel laser beams, exciting surface waves high in amplitude, and thereby detecting the surface waves by a heterodyne interference meter. CONSTITUTION:Laser which is oscillated by an ultrasonic wave exciting laser 2, and reflected by a 50% reflecting mirror 9, and laser which transmits the reflecting mirror 9, and is shifted in frequency by a sound optical modulator 4, are irradiated to the same point of a measured material 1, and a scanning interference fringe is generated over an irradiated point so as to allow surface waves 16 to be excited, so that the surface waves thereby propagate over the surface of the material. A heterodyne interference meter 18 irradiates laser onto the material 1, which is oscillated by an exciting ultrasonic wave detecting laser 3, and reflected by a 50% reflecting mirror 13, allows laser which is affected by the surface waves 16 so as to be scattered, to interfer with laser which transmits the reflecting mirror 13, and is shifted in frequency by a sound optical modulator 5, receives the resultant by an photo detection element 6, and it is detected 8 as a beat signal. The detection of the phase of the aforesaid signal enables the displacement of the material 1 caused by the excited surface waves to be measured. |
