Enhancement in flaw detectability by means of lockin temporal speckle pattern interferometry and thermal waves

A lockin method which takes into account the contribution of several modes from the Fourier spectrum generated by a heat load following a triangular waveform is used in temporal speckle pattern interferometry (TSPI) for the nondestructive detection of defects. By defining a parameter to quantify defect detectability, it is demonstrated that the use of this technique improves the detection of hidden flaws located in metal plates.