Quantitative detection of internal defects in objects using holographic double exposure

•This paper presents a novel approach by integrating the holographic double exposure method with image processing. We achieve both qualitative and quantitative detection of internal defects in objects.•The experimental results presented in this paper unequivocally demonstrate the efficacy and viability of the proposed method in detecting internal defects within objects.•This method requires the recording of just two holograms in distinct states in order to acquire the information regarding internal defects.•Compared with traditional methods, this method can obtain defect information faster and more accurately. Recent years have witnessed an increasing demand for high-quality materials in all industries; therefore, internal defects are disastrous for maintaining the required industrial quality. In this study, qualitative and quantitative analysis of the internal defects of objects is conducted using differential holographic double-exposure and digital image processing techniques. The objects underwent thermal loading, and two holograms were recorded at different temperatures. Internal defects were qualitatively and quantitatively analysed by processing and comparing the interference fringes produced by removing and reproducing the two holograms via digital image processing. The fringes at the location of the sample defects differed from the changes in surrounding fringes, and the defect size was determined by fitting the fringe region at the defect location. Finally, the experimental results were validated using a structured light 3D measurement method to identify the size of the defects. Interesting results were obtained, with a maximum error of 9.637 % for irregular defects and a minimum error of 3.528 % for regular defects.