Integrating photoluminescence with DIC for three-dimensional temperature and deformation field measurements in cryogenic environments

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In aerospace engineering and clean energy, many components operate under cryogenic conditions. Accurate surface temperature and deformation measurements are essential for monitoring service status, understanding thermomechanical behavior, and damage evolution of materials and structures at extremely low temperatures. In this study, a novel optical fusion measurement method, PhotoLuminescence-enabled Biprism Single-Lens 3DDIC (PL-BSL-3DDIC), is proposed, validated, and demonstrated. This method enables the acquisition of three-dimensional surface temperature, deformation fields, and morphology in cryogenic environments. By integrating the biprism-based 3D Digital Image Correlation (DIC) with fluorescence intensity ratio (FIR) thermometry, and utilizing the multifunctionality of the fluorescent thermometric deformation carrier (TDC), intrinsically synchronous and decoupled multi-channel data can be obtained. Key aspects, including the optical setup, computational workflow for result extraction, and temperature sensitivity of the TDC, are systematically discussed. An FIR thermometry model based on bi-telecentric optics is established for solid surface measurements, demonstrating effective decoupling of the resulting channels. The BAM:Eu²⁺ phosphor TDC was prepared and characterized, with its spectral properties used to optimize the filter transmission bands, ensuring optimal measurement performance across all channels. Calibration and validation experiments were conducted to verify the proposed thermometry model and systematically evaluate the method's performance, confirming its temperature sensitivity over 25K to 621K. In long-term tests (over 26 hours, 60K to 240K), the system achieved a mean absolute error (MAE) of less than 0.9K and a repeatability coefficient ( R F I R ) >99.7%. As a practical application, the cryogenic thermal expansion behavior of nickel-based alloys was accurately characterized using this method alone, with results closely aligning with reference data. The proposed methodology and procedures provide a robust tool and, more importantly, an extendible framework for comprehensive measurements under cryogenic or other required environments, while maintaining full compatibility with existing DIC techniques.