Fig. 1. Schematic diagram of watershed segmentation

Fig. 2. Schematic diagrams of point cloud processing. (a) Equidistant stratification; (b) find fitting axis through each layer’s centroid points

Fig. 3. Schematic diagrams of lens samples to be tested, test equipment, and scanning. (a) 1^#‒6^# diamond refractive lens samples processed by femtosecond laser; (b) synchrotron radiation X-ray CT experimental device; (c) schematic diagram of X-ray CT scanning of refractive lens

Fig. 4. CT image processing of lens sample. (a) Schematic diagram of CT projection image; (b) incomplete global threshold segmentation result (left) and ideal segmentation result (right); (c) 3D surface reconstruction

Fig. 5. Point clouds of paraboloid. (a) 1^# sample; (b) 2^# sample; (c) 3^# sample; (d) 4^# sample; (e) 5^# sample; (f) 6^# sample

Fig. 6. Fitting calculation process of mutual tilt angle. (a) Centroid distribution of 3^# sample divided into 100 layers; (b) two fitting lines

Fig. 7. Centroid distributions of different layers of 3^# sample. (a) 50 layers; (b) 100 layers; (c) 150 layers; (d) 200 layers; (e) 250 layers; (f) 300 layers

Fig. 8. Calculated value of mutual tilt angle varying with number of layers

Fig. 9. Surface recovery and fitting residuals of 6^# sample. (a)(b) Profiles of upper and lower paraboloids; (c)(d) fitting residuals of upper and lower paraboloids

Fig. 10. Test results obtained by laser scanning confocal microscopy for 6^# sample. (a)(b) Paraboloid surfaces of upper and lower paraboloids; (c)(d) fitting residuals of upper and lower paraboloids

Fig. 11. Comparison of calculated curvature radii based on CT and LSCM data. (a) Data of upper paraboloid; (b) data of lower paraboloid