Fig. 1. Formation principle of the distortion^[22]

Fig. 2. Distortion of the optical system. (a) Radial symmetry distortion (k1=-0.5); (b) decentering distortion（p1=p2=0.5）

Fig. 3. Imaging results of the optical system. (a) Imaging result of an optical system without distortion; (b) imaging result of an optical system with positive distortion (k1=0.5); (c) imaging result of an optical system with negative distortion (k1=-0.5)

Fig. 4. Radial distortion component and tangential distortion component in decentering distortion

Fig. 5. Schematic diagram of actual imaging position and ideal imaging position

Fig. 6. Distortion detection principle of the lithography projection objective

Fig. 7. Diagram of the distortion measurement device of lithography projection objective

Fig. 8. Flow chart of distortion measurement based on exposure

Fig. 9. Inter-field error and intra-field error^[36,41]

Fig. 10. Box measurement mark^[2]

Fig. 11. Shear exposure field. (a) X shear exposure field; (b) Y shear exposure field^[2]

Fig. 12. Schematic diagram of exposure distortion measurement of the SMEE^[3]

Fig. 13. Schematic diagram of aerial image position measurement based on slit scanning method^[4]

Fig. 14. Distortion detection based on aerial image^[6]

Fig. 15. Principle of the differential measurement^[14]

Fig. 16. Principle of the Shaker-Hartmann sensor. (a) Ideal wavefront; (b) deformed wavefront^[11]

Fig. 17. Principle of measuring the position deviation of the marked image point with the Shake-Hartmann sensor. (a) Horizontal; (b) vertical^[15]

Fig. 18. Principle of the SMEE interferometer^[45]

Fig. 19. Optical path diagram of the point diffraction interferometer for measuring distortion^[16]

Fig. 20. Wave aberration detection system of projection objective based on Ronchi shearing interference^[51]

Fig. 21. Schematic diagram of the measurement grid^[19]

Fig. 22. Reticle alignment marks (2×7) on both ends of the mask are used to align the reticle^[52]

Fig. 23. Principle of measuring distortion of the projection objective of the lithography machine based on Moiré fringe^[53]