Research on Laser Ultrasonic Visual Image Processing

Guided ultrasonic waves propagation imaging: a review

“…In other cases, when there is too much speckle noise and hinders the detection of small damage, a median filter or other moving-window filters (convolution) would help [307,308]. Removal of the speckle noise based on local statistics filtering with a least-square estimation of first-order Taylor series expansion of an image had been proposed too [309]. DL methods could be investigated more as well [310].…”

“…On the other hand, if the objective is to accentuate damage, then a blob detection mask (moving window) based on Laplacian filter L, such as the one shown in equation (31), can be used [167]. Other forms of Laplacian filter are available and discussed in [309]. If a quantitative evaluation of the image clarity is needed, then perhaps the entropy and the average gradient of an image can be used, as demonstrated by Hongling et al [309].…”

“…Other forms of Laplacian filter are available and discussed in [309]. If a quantitative evaluation of the image clarity is needed, then perhaps the entropy and the average gradient of an image can be used, as demonstrated by Hongling et al [309].…”

“…The applications for the inspection of metallic specimens are tabulated in table 5, while for composite specimens are in table 6. These tables give the Thick plate/structures Welding crack in steel [220,317,318] The specimen was immersed under oscillating water [77, 320] Welding with blind and through holes [309] Fatigue crack in aluminum [115] Fuselage Additive manufacturing Heterogeinity/imperfect powder melting/micro void [344,346,384] inspections for simple plate specimens first, followed by more complicated structural specimens. Works in which the G-UPI had been applied for detecting or evaluating a specific type of damage in a specific type of specimen are given in the last column of the tables so that the readers can find detailed information easily if needed.…”