Fig. 1. Annular force variable curvature mirror developed by our group and deflection testing results^[25]

Fig. 2. Strain comparison of finite element analysis after deflection. (a) Strain of annular force variable curvature mirror; (b) strain of variable curvature mirror with variable thickness under uniform force driving

Fig. 3. Experimental systems of variable curvature mirror with variable thickness under uniform pressure. (a) Model and prototype of variable curvature mirror with variable thickness; (b) actuation system of variable curvature mirror

Fig. 4. Surface accuracy of variable curvature mirror with 100 mm diameter under 0.07 MPa

Fig. 5. Optical design of 5× zoom opical system and corresponding parameters

Fig. 6. Central deflection curves of 1st and 4th mirrors. (a) 1st mirror; (b) 4th mirror

Fig. 7. Comparison of thickness distributions before and after optimization

Fig. 8. Structure parameters of optimized variable curvature mirror

Fig. 9. Design of one space optical system

Fig. 10. Changes of MTF under focusing and 4 mm defocusing. (a) Focusing; (b) 4 mm defocusing

Fig. 11. Correspondence between deflection of focusing vector height of secondary mirror and defocus amount. (a) Correspondence between needed deflection of focusing vector height of secondary mirror at focusing position and defocus amount; (b) correspondence between needed deflection of focusing vector height of two adjacent positions and defocus amount

Fig. 12. Comparison between MTF corresponding to ideal in-focus and MTF for 4 mm defocusbeing compensated through variable curvature secondary mirror。(a) MTF of ideal in-focus; (b) MTF after focusing compensation

Fig. 13. Process of variable curvature mirror scanning MTF of equivalent encoding imaging

Fig. 14. MTF of equivalent encoding imaging under defocus of 0-30. (a) MTF of large focal depth space camera system; (b) equivalent OTF for different focal depth extended range

Fig. 15. Equivalent PSF of secondary mirror modulation coding and PSF of cubic phase coding. (a) Equivalent PSF of secondary mirror modulation coding; (b) PSF of cubic phase coding

Fig. 16. Comparison of equivalent MTF between large depth-of-focus system and classical cubic phase encoding