Precision Measurement Method for High-order Aspheric Surface Based on Pinhole Point Diffraction Interferometry and Optimized Sub-aperture Stitching

To address the challenges of insufficient accuracy and poor versatility faced by conventional interferometers in measuring high-order aspheric surfaces, this paper proposes an optimized annular sub-aperture stitching method based on a reverse global planning strategy. The method initiates sub-aperture division from the edge region with the highest asphericity, aiming to maximize the effective measurement range of each individual sub-aperture and setting the minimization of the number of sub-apertures (N) as the core optimization objective. The algorithm features a concise structure, high stability, and ease of automation, enabling a significant extension of the interferometer's dynamic measurement range. Simulation studies demonstrate that the method effectively reduces the required number of sub-apertures, thereby suppressing the propagation and accumulation of mechanical positioning errors during the stitching process. Furthermore, by integrating this method with pinhole point diffraction interferometry (PPDI), a measurement system combining high accuracy and large measurement range is constructed. Experimental measurements of a convex high-order aspheric surface yield stitched results that are in excellent agreement with full-aperture measurements, with the peak-to-valley (PV) deviation of only 2.66 nm and the root-mean-square (RMS) deviation of only 0.44 nm. A detailed uncertainty analysis of the system confirms the reliability and reproducibility of the measurement results. This study not only provides an efficient method for the precision measurement of aspheric surfaces with large deviations but also offers a new technical pathway for enhancing the measurement capability and automation level of interferometers.