Laser ultrasonic microscopy

Imaging of transient surface acoustic waves by full-field photorefractive interferometry

“…[1][2][3][4][5][6] Moreover, possible bandwidth limitations of electronic detection can be circumvented by making use of an optical delay line. 7,8 Optical detection of SAW induced displacements at a single location can be done with high sensitivity, e.g., by interferometric detection, 9,10 laser beam deflection, 11,12 modulated optical reflection, 13 or heterodyne diffraction detection. 14 Single SAW signals contain valuable information on the SAW velocity and attenuation, which are related to the elasticity and microstructure of the materials.…”

“…14 Single SAW signals contain valuable information on the SAW velocity and attenuation, which are related to the elasticity and microstructure of the materials. 6,9,12,15,16 By analyzing signal contributions due to SAW mode conversion at defect related elastic discontinuities along the path between the excitation a) Authors to whom correspondence should be addressed. Electronic addresses: xdxu@nju.edu.cn and christ.glorieux@fys.kuleuven.be and detection locations, the presence and the size of the defects can also be assessed.…”

High-speed non-contact defect imaging for a plate-like structure

“…Many publications can be found on laser ultrasonics, in which elastic wave, usually ultrasonic range, is generated by a pulse laser and the vibration is detected with laser interferometry [14][15][16][17][18][19][20][21][22][23]. The laser ultrasonics have also been applied to non-destructive evaluation of thin plates for a long time; for example, Hutchins et al elaborated Lamb wave propagation generated with a laser and showed that the measurements of Lamb waves enable to estimate the plate thickness and their elastic constants [15].…”

“…Thereafter, many works were carried out on Lamb waves generated with a laser because an A0 mode of Lamb waves can be generated with relatively large amplitude by laser emission on a plate surface [16][17][18]. Moreover, non-contact measurements using a laser have also been investigated for imaging material characteristics and defects in a material, in which spatial information was collected by scanning both lasers for generation and detection (or a specimen) [19][20][21].…”