“…Hence, different types of thermographic image analysis methods have been proposed for signal enhancement, e.g. thermographic signal reconstruction (TSR) [19,20], differential absolute contrast (DAC) [21,22], pulsed phase thermography (PPT) [23,24], principal component thermography (PCT) [25], etc., where TSR is frequently used for its performance in data compressing and noise reduction. Based on the Fourier diffusion equation, TSR applies polynomial filters to eliminate the noise contained in thermographic data.…”