“…In recent years, due to the quick, full-field and non-contacted detection capabilities [16,17], infrared thermography (IRT) has been used in human medicine [18,19], aerospace material [20], building diagnostics [21,22], nuclear power transportation [23,24], etc. Compared with the passive IRT, the active one allows the inspection of objects which do not emit heat and allows more information about the defect (location and size) in just a few seconds [25,26]. Zhuo et al [27] had a size determination of interior defects by reconstruction of subsurface virtual heat flux, bringing an improvement in the detection of low width-to-depth ratio defects using IRT.…”