Study on imaging techniques and quantitative detection method for internal void defects in rubber based on terahertz reflection imaging

This paper applies the reflection mode of terahertz time-domain spectroscopy technology to conduct research on the void defects in black silicone rubber samples. Algorithms such as power spectral density (PSD) integration imaging, homomorphic filtering, and the Otsu method are innovatively integrated to construct an efficient, high-precision defect characterization system. Different from traditional research, this paper deeply explores the advantages of each algorithm and optimizes them according to the characteristics of rubber materials and terahertz signals. By combining multiple features in the time-domain and frequency-domain to reconstruct terahertz images, and with the collaborative optimization of grayscale histogram equalization and filtering algorithms on the imaging quality, the optimal combination of PSD integration imaging, homomorphic filtering, and the Otsu method is determined, achieving precise defect imaging and quantification. In spectral analysis, a method combining wavelet signal denoising and time-domain spectroscopy is proposed. A formula based on time-of-flight was then used for quantitative analysis of the defects. In 3D imaging, an innovative alignment operation of denoised time-domain spectral curves is introduced. Combined with the maximum intensity projection, the clear visualization of void defects is realized.