Integrated wavefront detection for large-aperture segmented planar mirrors

To meet the testing requirements of next-generation large-aperture telescopes, conventional monolithic planar mirrors are inade-quate. Additionally, a large-aperture planar mirror should be used to achieve beam relays in large-aperture telescopes and auto-collimation testing during integrated detection. This study adopts a multimodal testing approach for flattening measurements of annularly segmented large-aperture planar mirrors. A segmented planar mirror with toroidal tape joining is considered to model and analyze the alignment, confocal, and co-phase measurements, as well as evaluate error transfer characteristics based on the transfer function. Simulation analysis and experimental verification are combined to demonstrate the principle of wavefront sensing and control for a large-aperture planar mirror. By implementing high-throughput high-signal-to-noise edge sensing for segmented mirrors along with a global control matrix and fast-solving algorithms for large-scale linear equations with multiple constraints. Consequently, near-zero-overshoot co-phasing maintenance and intersegment collision avoidance are achieved, minimizing interference with long-exposure observations during online adjustments. Additionally, small-aperture planar mirrors are used for autocollimation testing, in which their focal lengths establish the test optical path, and the optical lever effect of re-flectors enhances alignment sensitivity. By integrating autocollimation with wavefront sensing, high-precision control of co-focus, co-phasing, and surface deformation errors is accomplished.