Fig. 1. Optical layout design of the spaceborne telescope for TianQin Project

Fig. 2. The principle of the Shack-Hartmann wavefront sensor

Fig. 3. Image matching principle of correlation algorithm

Fig. 4. The process of wavefront reconstruction and the composition of reconstruction error

Fig. 5. The optical path diagram of the experimental platform

Fig. 6. Effective sub-aperture distribution of the point source image

Fig. 7. Individual sub-aperture image and noise calculation region (within the yellow box) and matching region (within the red box)

Fig. 8. The average shift measured on each frame image by employing the CFF and the TCoG algorithm. Defocus values are (a) 0 nm, (b) 0.22 nm, (c) 0.44 nm and (d) 0.66 nm

Fig. 9. Zernike defocus values, and their average calculated on each frame image by employing the CFF and the TCoG algorithm. Defocus values are (a) 0 nm, (b) 0.22 nm, (c) 0.44 nm and (d) 0.66 nm

Fig. 10. The average reconstructed wavefront using the CFF and the TCoG algorithm. Defocus values are (a) 0 nm, (b) 0.22 nm, (c) 0.44 nm and (d) 0.66 nm

Fig. 11. The residual wavefront generated using the CFF and the TCoG algorithm. Defocus values are (a) 0 nm, (b) 0.22 nm, (c) 0.44 nm and (d) 0.66 nm