Fig. 1. 2-D diagram of the optical system

Fig. 2. Modulation transfer function curves of the optical system

Fig. 3. Enclosed energy curves of the optical system

Fig. 4. Diagram of light-and-small metal-based optical system

Fig. 5. (a) Front view and (b) side view of primary mirror assembly

Fig. 6. Deformation of the primary mirror under its own gravity

Fig. 7. Secondary mirror assembly

Fig. 8. Shading baffle structure

Fig. 9. Results of mode analysis of the whole optial system

Fig. 10. Results of system static analysis under its own grarity

Fig. 11. Primary mirror assembly by additive manufacturing

Fig. 12. Secondary mirror assembly by additive manufacturing

Fig. 13. Shading baffle by additive manufacturing

Fig. 14. Primary mirror after SPDT and it′s surface shape data

Fig. 15. Secondary mirror after SPDT and it′s surface shape data

Fig. 16. Primary mirror surface observed by a high magnification camera

Fig. 17. Primary mirror modified by Ni-P coating

Fig. 18. Primary mirror and surface shape data after optical processing

Fig. 19. Second mirror and surface shape data after optical processing

Fig. 20. Primary and secondary mirrors after gold plating

Fig. 21. Surface quality of the primary mirror after gold plating

Fig. 22. Surface quality of the second mirror after gold plating

Fig. 23. Centering alignment experiment of the primary and secondary mirror assembly

Fig. 24. The performance test of the optical system

Fig. 25. The measurement result of the focal length

Fig. 26. MTF test results for different FOVs

Fig. 27. Weight test