High-temperature digital image correlation surface measurement method based on laser projection speckle

To address the oxidation and detachment of spray-applied speckles that undermine digital image correlation-based three-dimensional topography measurement at elevated temperatures, this study proposes a laser-projected speckle generation method using ground-glass diffusion. First, an integrated speckle evaluation framework is developed that combines single-image quality metrics-the multi-factor fusion index and its components-with a binocular-consistency metric based on zero-mean normalized cross-correlation. Second, the effects of laser parameters (power and wavelength), imaging parameters (aperture and exposure time), and optical spacing on speckle quality and digital image correlation stereo-matching accuracy are systematically analyzed at 1000°C, from which the optimal experimental settings are identified. Finally, quantitative and qualitative experiments show that, relative to coordinate-measuring machine results, the relative error at room temperature lies within 0%-2%, while at 1000°C it lies within 0%-9%. Furthermore, a surface point-cloud reconstruction of an engine turbine blade at 1000°C is demonstrated; despite local detail noise, the overall geometry is accurately recovered, confirming the engineering feasibility of the proposed method in extreme high-temperature environments.