Modified Pulse-Phase Thermography Algorithms for Improved Contrast-to-Noise Ratio from Pulse-Excited Thermographic Sequences

Two modified algorithms for pulsed phase thermography were defined. The principle is to mask out parts of the thermal signal that only add noise but contain no significant information. A first algorithm uses a frequency dependent Gaussian window function. A second algorithm leads to a rectangular window function. The algorithms were tested on synthetic signals modeling a circular hidden defect in a plate and experimentally by flash excited thermography on a steel and a polymer sample. For both materials, a significant improvement of the contrast-to-noise ratio from the defects was obtained for higher analysis frequencies.