Cost-Effective Digilog Chirp Thermal Wave Imaging System for Composite Subsurface Evaluation

Thermal wave imaging has emerged as a promising nondestructive evaluation tool for evaluating the subsurface integrity of objects due to its noncontact, wholefield, and remote evaluation procedure. However, the cost, lab-based installation, and stringent testing requirements of conventional thermal wave imaging systems limit their applicability and make them ineffective in testing at semi-closed and high-altitude environments. The development of lowcost, compact imaging systems with enhanced resolution to facilitate remote accessibility for in situ inspection has become a challenging task while considering the cost, size, and resolution of existing thermal imaging systems. This article introduces a low-cost digital chirp modulated active thermal wave imaging system for detecting subsurface anomalies using dedicated stimulation and processing approaches, aimed at enhancing spatial and depth resolutions, as well as improving depth scanning capabilities. This cost-effective compact thermal wave imaging system controlled by a Raspberry Pi facilitates enhancement of depth scanning through pulse compression friendly digilog chirp-based stimulation along with an enhanced spatial resolution from deep learning ESRGAN-based fourfold super-resolution imaging, mimicking a traditional IR imaging system. Laboratory-based experimental outcomes confirmed its applicability for testing of composites, and its performance is evaluated using various quantitative thermographic and image processing-based metrics.