Multi-field split curvature wavefront sensing and its application in the large field survey telescope

Abstract The image quality of a large field survey telescope with a fast focus ratio of the primary mirror is high sensitivity to the optical elements' misalignments and the primary mirror's deformations. To maintain high optical performance, the perturbations need to be aligned, and the tomographic reconstruction of these perturbations can be derived from wavefront sensing with multi-field points for alignment. This work undertakes a comprehensive examination related to the implementation and optimisation of a multi-field split curvature wavefront sensing system, including defocus distance, signal pre-processing, deblending of overlapped doughnuts, field-dependent correction, and distorted coordinate correction. We also conduct experiments to demonstrate the application and performance of a multi-field split curvature wavefront sensing system in Mephisto. In the context of the decentering of the secondary mirror, the coefficient of determination (R²) attains a high value of 0.993, indicating a robust linearity between the coma coefficients and the decentering of the secondary mirror. A comparative analysis of the simulated and experimental results shows that the difference between them is less than 0.1 λ.