Fig. 1. Paul Baker three-mirror system

Fig. 2. Willstrop Mersenne–Schmidt three-mirror system

Fig. 3. LSST optical system^[3]

Fig. 4. Rumsey optical system^[4]

Fig. 5. Korsch coaxial three-mirror system

Fig. 6. Two-axis three-mirror system proposed by Korsch in 1972^[8]

Fig. 7. Korsch two-axis three-mirror system

Fig. 8. Two-axis three-mirror optical system I proposed by Korsch in 1977^[10]

Fig. 9. Optical system of HiRISE

Fig. 10. Two-axis three-mirror optical system II proposed by Korsch in 1977^[10]

Fig. 11. Optical system of SNAP^[12]

Fig. 12. Zucchi’s front-view reflecting telescope^[13]

Fig. 13. Schiefspiegler optical system

Fig. 14. Buchroeder Tri-Schiefspiegler

Fig. 15. Solano Tri-Schiefspiegler

Fig. 16. Transformation process from coaxial system to off-axis system^[15]

Fig. 17. [in Chinese]

Fig. 17. Configurations of Zero-Petzval off-axis TMA optical system

Fig. 18. Triplet lenses optical system

Fig. 19. Non-re-imaging Wetherell TMA optical system

Fig. 20. Freeform off-axis TMA optical system with ultrawide field of view^[20]

Fig. 21. Cook TMA optical system with real pupil^[21]

Fig. 22. Hallam system (Hughes Walrus system)^[22]

Fig. 23. Non-re-imaging Walrus TMA optical system

Fig. 24. Inverse telephoto optical system

Fig. 25. Re-imaging Cook TMA optical system^[25]

Fig. 26. Optical system of high resolution imaging camera on “Tianwen-1” mission

Fig. 27. Re-imaging TMA optical system with relayed image plane between primary mirror and secondary mirror

Fig. 28. Off-axis compact TMA optical system^[32]

Fig. 29. Re-imaging wide field of view off-axis Cook TMA optical system

Fig. 30. Off-axis TMA optical system proposed by Rodgers

Fig. 31. Compact off-axis three-mirror reflective optical system^[35]

Fig. 32. Layout of freeform off-axis optical system^[36]

Fig. 33. Optical system forming process^[36]

Fig. 33. [in Chinese]

Fig. 34. Off-axis TMA optical system proposed by Cook in 1994^[37]

Fig. 35. Off-axis TMA system proposed by Cook in 1996^[38-39]

Fig. 36. Off-axis TMA optical system with folding mirror (I)

Fig. 37. Off-axis TMA optical system with folding mirror (II)

Fig. 38. Afocal TMA optical system proposed by Abe Offner: (a) Coaxial configuration; (b) Coaxial configuration; (c) Off-axis configuration^[40]

Fig. 39. Coaxial afocal TMA optical system

Fig. 40. Off-axis afocal TMA optical system

Fig. 41. Off-axis afocal TMA optical system proposed by Cook^[41]