Toroidally focused sensor array for real-time laser-ultrasonic imaging: The first experimental study

Non-destructive laser-ultrasonic Synthetic Aperture Focusing Technique (SAFT) for 3D visualization of defects

“…The Synthetic Aperture Focusing Technique (SAFT) is one of the imaging algorithms [1] for generating 2D and 3D imaging of defects by synthesizing ultrasonic signals from small aperture transducer(s) to improve the lateral resolution using point-by-point scanning. SAFT algorithms can be categorized as the Time domain SAFT (T-SAFT) [1] , [7] and Frequency domain SAFT (F-SAFT) algorithms [8] , [9] , [10] , [11] , [12] , [13] , [14] , [15] . Compared with the T-SAFT, rapid implementation is an important advantage of F-SAFT when it is used in practical situations [1] , [7] , [8] , especially real-time imaging.…”

“…The LU techniques have characteristics such as non-contact and non-destructive testing [3] , [4] , [5] , and can be conducted in wide frequency bands, on curved complex surfaces, or in hostile environments [6] , [8] . Successful demonstrations have been produced for detecting cracks in stainless steel plates [16] and imaging the layering of curved interfaces [9] , [10] using the LU-SAFT.…”

“…The algorithm was also applied to detecting and imaging of other industrial devices and complex structures [17] . More applications can be found in the field of Photoacoustic imaging [7] , [8] . To date, to the best of our knowledge, applications of the LU-based SAFT method require coincident generation and detection by focusing on the same point, ablative generation using point laser sources, resulting in destructive specimen testings [2] , [9] , [10] , [11] , [13] , [14] , [15] , [16] , [17] , [18] , [19] .…”