Fig. 1. Basic principle of plane sub-aperture stitching interferometer

Fig. 2. Stitching of three sub-apertures

Fig. 3. Original surface and sub-aperture segmentation surfaces

Fig. 4. Stitching error distribution of W1、W2、W3. (a) Difference between W1,W2,W3 and W0; (b) difference between W1, W2, W3 each other

Fig. 5. Stitching error results of surfaces constructed with different Zernike polynomials

Fig. 6. Stitching error while the positioning error is one pixel

Fig. 7. (a) Overlap area in adjacent sub-apertures and its corresponding (b) reference surface error

Fig. 8. Stitching results of different Zernike aberrations. (a) Z4; (b) Z6; (c) Z10; (d) Z16

Fig. 9. Stitching accumulation errors of Z4-Z20 Zernike aberrations

Fig. 10. Stitching coefficient error of different sub-apertures under random noise. (a) Sub2; (b) Sub3

Fig. 11. Stitching error of the random noise of different standard deviations. (a) Standard deviations between 0-1; (b) standard deviation of 0.1

Fig. 12. High order noise during the subaperture measurements. (a) Difference between the second and the first measurements;(b) difference between the third and the second measurements; (c) difference between the forth and the third measurements; (d) difference between the fifth and the forth measurements

Fig. 13. Stitching accumulation errors of 36 high order random noise

Fig. 14. Stitching measurement results of the 450 mm×60 mm flat mirror surface. (a) 15 sub-apertures with double sub-aperture stitching algorithm; (b) 8 sub-apertures with double sub-aperture stitching algorithm; (c) 15 sub-apertures with error averaging stitching algorithm; (d) 15 sub-apertures with double sub-aperture stitching algorithm after removing the high order errors of reference surface; (e) 15 sub-apertures with double sub-aperture stitching algorithm after removing the second order errors of