Fig. 1. Ruby ball measurement system device diagram

Fig. 2. Flowchart of the algorithm for Canny edge detection using adaptive thresholds

Fig. 3. Ruby original image and edge image

Fig. 4. Flow chart of quadratic edge detection algorithm based on image fusion and cubic spline interpolation

Fig. 5. Edge map comparison after two edge detections

Fig. 6. Schematic diagram of coordinate offset solution

Fig. 7. Gradient magnitude of the edge points is interpolated

Fig. 8. Quadratic curve fitting at （635，925）

Fig. 9. Ruby ball measurement results map

Fig. 10. Comparison of the results of three methods

Fig. 11. Localization errors measured at different gains and different SNRS