We propose a non-contact displacement measurement method for various materials based on laser-induced ultrasound. We illuminate nanosecond pulse laser to a material surface. The various kinds of elastic waves whose maximum frequency is several hundred MHz are excited by laser-induced ultrasound. And then, only elastic waves which depends on the thickness of specimen remains selectively. The elastic waves occur displacement. We propose the collector optics type Twyman-Green interferometer as non-contact measurement method for displacement of rough surface. Using the aluminum whose thickness is 1.0 mm, we can detect the resonance signal of elastic waves and the resonance frequency that is 3.8 MHz by FFT.
