Fig. 1. Principle of annular sub-aperture scanning method for measuring axicon surface

Fig. 2. Schematic of using interferometer to measure axicon surface. (a) Optical path difference when axicon surface is measured by interferometer; (b) measured interferogram of axicon

Fig. 3. Principle of data interpolation-stitching of axicon surface

Fig. 4. Simulated interferograms of axicon. (a) Ideal interferogram of axicon in simulation; (b) interferogram of axicon with translation and tilt errors in simulation

Fig. 5. Change of optical path during scanning of axicon

Fig. 6. Interferograms of concave axicon for different diameters. (a) 4 mm; (b) 28 mm; (c) 100 mm; (d) 148 mm

Fig. 7. Interference fringe contrast of axicon for different diameters

Fig. 8. Interferograms of convex axicon for different diameters.(a) 3.2 mm; (b) 8.3 mm; (c) 10.9 mm; (d) 22.4 mm

Fig. 9. Tangential (lateral) resolution on axicon surface at different radial positions

Fig. 10. Schematic of horizontal measured area under focal depth limitation

Fig. 11. Radial measured area at different cone angles

Fig. 12. Maximum measurable diameter can be tested at different cone angles under interference contrast limitation

Fig. 13. Measurable aperture range of axicon under tangential surface error limitation

Fig. 14. Schematic of coordinate distortion in extreme value pixel ring

Fig. 15. Measuring surface of convex axicon. (a) Experimental setup; (b) principle of optical path of experiment

Fig. 16. Interferograms and phase maps at different scanning positions. (a) 2 mm; (b) 8 mm; (c) 14 mm

Fig. 17. Measurement results of axicon surface. (a) By annular sub-aperture scanning method; (b) by annular sub-aperture scanning method with 90° rotation of axicon; (c) by LuphoScan profiler

Fig. 18. Measurement result of axicon surface in area within 1.3-mm width near center