Fig. 1. Edge error detection structure of segmented-mirror based on equal thickness interference

Fig. 2. Segmented-mirror measurement based on equal thickness interference principle

Fig. 3. Light intensity distribution of two sub-mirrors without segment error

Fig. 4. Light intensity distribution when the two sub-mirrors have relative errors. (a) x-axis tip error; (b) y-axis tilt error; (c) piston error

Fig. 5. Gray value liner fitting on the center line of Newton ring. (a) Newton ring corresponding to the left sub-mirror; (b) Newton ring corresponding to the right sub-mirror with 35 nm piston error

Fig. 6. Change of radius of Newton ring with piston error

Fig. 7. Changes in the position of the optical flat and the equivalent aperture after the piston error of the two mirrors. (a) No error between the two sub-mirrors; (b) a piston error between the two sub-mirrors

Fig. 8. Hough test results when there is a tilt error between the two sub-mirrors. (a) 2-1 Hough test result; (b) improved Hough concentric circle test result

Fig. 9. Interference image of equal thickness when the installation translation error of optical flat is 3 mm

Fig. 10. Interference fringe images of equal thickness when there is an overall tilt error. (a) Existing a tilt error of 10″ along the x-axis; (b) existing a tilt error of 10″ along the y-axis