Experimental investigation on noise rejection capabilities of pulse compression favourable frequency-modulated thermal wave imaging

Abstract

Among the various non-destructive testing and evaluation methods, infrared thermography gained its importance due to its fast, whole field, remote and quantitative evaluation capabilities for inspection of various materials. Being an optimum technique in terms of usage of low peak power heat sources in a moderate experimentation time, frequency-modulated thermal wave imaging (FMTWI) plays a vital role in the infrared thermographic community. The noise rejection capabilities of the proposed pulse compression favourable FMTWI by using principal component analysis as a post-processing technique are highlighted. The proposed scheme has been tested on a mild-steel sample having sub-surface flat bottom hole defects located inside the test specimen at various depths. It is clear from the obtained results that the reconstructed pulse (main lobe) concentrates much of the imposed energy into a narrow duration, which enhances the defect detection sensitivity and resolution in order to visualise the subsurface defects with higher signal-to-noise ratio