Significance The preservation of cultural heritage increasingly requires non-contact, non-invasive, and physically interpretable diagnostic methods. Infrared Thermography (IRT), which captures transient surface temperature responses induced by controlled thermal excitation, has emerged as a powerful tool for revealing subsurface structures and material heterogeneities. Unlike purely optical imaging techniques, IRT is sensitive to heat transfer behavior, enabling indirect access to thermophysical properties and interfacial conditions. These characteristics make IRT particularly suitable for the investigation of complex, fragile, and multilayered heritage objects. In recent years, its role has gradually shifted from qualitative anomaly visualization toward physically informed analysis, motivating the need for a systematic review of methodological developments and application trends.

Progress This review summarizes recent advances in active IRT for nondestructive testing of cultural heritage, covering metallic artifacts, composite layered objects, organic fiber-based materials, and porous inorganic materials. From a methodological perspective, progress can be understood along three interconnected dimensions: heat transfer modeling, signal processing, and multimodal data integration.　　Early applications primarily focused on enhancing thermal contrast to visualize hidden structures such as voids, inclusions, and repairs. Subsequent studies introduced one-dimensional and multilayer heat transfer models to associate thermal responses with parameters such as thermal diffusivity and interfacial thermal resistance, enabling semi-quantitative interpretation of material states. For layered cultural objects, model-based analysis has been used to diagnose delamination and bonding conditions, while for metallic artifacts, thermophysical parameter variations have provided insights into casting structures and restoration regions.　　More recently, studies have increasingly integrated three-dimensional geometric information, numerical simulations, and data-driven processing, which has further expanded the analytical capability of IRT. Geometric compensation and multiphysics modeling help separate shape-induced thermal effects from intrinsic material variations, improving the reliability of parameter inversion. In the case of organic heritage materials such as paper-based artifacts, research has established low-energy excitation protocols and safety evaluation frameworks, demonstrating that IRT can reveal internal reinforcements and subtle layer separations without compromising material integrity. For stone and other porous materials, IRT has been applied to monitor the evolution of thermophysical properties during aging processes, linking thermal behavior to microstructural changes.

Conclusions and Prospects Overall, IRT in cultural heritage research has evolved from a visualization-oriented inspection technique into a physically grounded diagnostic approach capable of supporting material characterization and process-related interpretation. Despite this progress, challenges remain in model applicability under complex geometries, uncertainty in linking thermal signals to microstructural parameters, and the lack of standardized testing protocols.　　Future developments are expected to focus on deeper coupling between heat transfer modeling and data-driven methods, improved integration with three-dimensional and multimodal measurements, and the establishment of material-specific safety and evaluation standards. With these advances, IRT is poised to play an increasingly important role in preventive conservation, condition assessment, and the scientific study of historical materials and technologies.