Non-destructive evaluation of the distribution of stress by means of the photoacoustic microscope

For inspection or quality control of various materials and safety of moving machine parts or of buildings, it is very important to measure the distribution of stress non-destructively. There exist a few methods for measuring the distribution of stress: the ultrasonic method, Raman microscopy and X-ray diffraction. But these conventional methods are limited to certain samples or measuring conditions. On the other hand, photoacoustic microscopy (PAM), generating an elastic wave directly in a sample by the photoacoustic effect [1], should be able to measure an elastic property such as the distribution of stress without limitations on a sample [2,3].