Fig. 1. Schematic diagram of common interpolation algorithms

Fig. 2. Flowchart of interpolation calculation after denoising

Fig. 3. Flowchart based on edge gradient direction interpolation

Fig. 4. Edge fitting models

Fig. 5. Flowchart for locating sub-pixel edges using fitting method

Fig. 6. Ideal two-dimensional step model

Fig. 7. Flowchart of classic sub-pixel edge localization using moment method

Fig. 8. Calculation process for mask of Zernike moment A11^［45］

Fig. 9. Flow chart of improved Zernike moment method

Fig. 10. Edge models^［50］