Fig. 1. Examples of mirror optimization overseas

Fig. 2. Examples of mirror optimization in domestic

Fig. 3. Flow chart of topology optimization design

Fig. 4. Optical path diagram of coaxial four-mirror system

Fig. 5. Initial finite element model of topology optimization

Fig. 6. Density distribution diagram of materials by topology

Fig. 7. Distribution results of density greater than 0.6 kg/m²

Fig. 8. Mesh model for size optimization

Fig. 9. Results of free size optimization

Fig. 10. Final design of primary-fourth mirror model

Fig. 11. The first-order vibration mode

Fig. 12. The second-order vibration mode

Fig. 13. The third-order vibration mode

Fig. 14. Cloud atlas of surface shape for primary-fourth mirror

Fig. 15. Testing process of surface shape by interferometer detection

Fig. 16. Test results of surface shape for primary-fourth mirror