Cross‐Scale High‐Precision Characterization for Three‐Dimensional Profiles of Curved Diffractive Microstructures

Macroscopic substrate surface errors and microscopic groove parameters influence the optical performance of curved diffractive microstructures. However, existing profile measurement techniques face a trade-off between large-area coverage and high resolution, which limits the ability of conventional two-dimensional (2D) line-profile methods to capture the global grating morphology. To address existing limitations, this study proposes a three-dimensional (3D) profile characterization method for curved gratings across macro- and micro-scales. Seamless reconstruction of full-aperture 3D topography with submicron-scale features was achieved using laser scanning confocal microscopy-based stitching measurements. Preprocessing for feature extraction was then performed using frequency-domain separation and the iterative closest point algorithm. The 2D Gabor filter bank, traditionally used for image texture feature extraction, was extended to 3D space to precisely characterize the period distribution of the microstructures. When combined with local planar least-squares fitting, the method enables precise characterization of the 3D spatial distribution of the grating blaze angle. Experimental results demonstrate close agreement between 3D and 2D characterization, with deviations below 0.01 µm in mean period and 0.05° in mean blaze angle, confirming the accuracy and reliability of the method. This study overcomes the limitations of conventional 2D line-profile analysis by enabling high-precision, cross-scale 3D global characterization of curved diffractive microstructures, supporting process optimization and quality control in advanced optical manufacturing.