Application of Terahertz Detection Technology in Non-Destructive Thickness Measurement

Terahertz (THz) waves, situated between the infrared and microwave regions, possess distinctive properties such as non-contact, high penetration, and high resolution. These properties render them highly advantageous for non-destructive thickness measurement of multilayer structural materials. In comparison with conventional ultrasound or X-ray techniques, THz thickness measurement has the capacity to acquire thickness data for multilayer structures without compromising the integrity of the specimen and is characterized by its environmental sustainability. The extant THz thickness measurement techniques principally encompass time-domain spectroscopy, frequency-domain spectroscopy, and model-based inversion and deep learning methods. A variety of methodologies have been demonstrated to possess complementary advantages in addressing subwavelength-scale thin layers, overlapping multilayer interfaces, and complex environmental interferences. These methodologies render them suitable for a range of measurement scenarios and precision requirements. A wide range of technologies related to this field have been applied in various disciplines, including aerospace thermal barrier coating inspection, semiconductor process monitoring, automotive coating quality assessment, and oil film thickness monitoring. The ongoing enhancement in system integration and continuous algorithm optimization has led to significant advancements in THz thickness measurement, propelling it towards high resolution, real-time performance, and intelligence. This development offers a wide range of engineering applications with considerable potential for future growth and innovation.