Fig. 1. Femtosecond laser ablation platform

Fig. 2. Two forms of light spot at different powers. (a) 10 mW;(b) 20 mW;(c) 50 mW

Fig. 3. Classification process of cascaded SVM

Fig. 4. Centroid coordinates of sequential spots at different powers. (a) 10 mW; (b) 20 mW; (c) 50 mW

Fig. 5. First-level SVM classification results under different powers. (a) 10 mW; (b) 20 mW; (c) 50 mW

Fig. 6. Way of upper and lower peer lines

Fig. 7. Standard models at different powers. (a) 10 mW; (b) 20 mW; (c) 50 mW

Fig. 8. SSIM values of E spot at different powers. (a)10 mW; (b) 20 mW; (c) 50 mW

Fig. 9. Cascade SVM classification results at different powers. (a) 10 mW; (b) 20 mW; (c) 50 mW

Fig. 10. Classification results of different methods at 10 mW power. (a) HOG-SVM method; (b) LBP-SVM method; (c) GP-SVM method; (d) accuracy comparison curves of four methods

Fig. 11. Classification results of different methods at 20 mW power. (a) HOG-SVM method; (b) LBP-SVM method; (c) GP-SVM method; (d) accuracy comparison curves of four methods

Fig. 12. Classification results of different methods at 50 mW power. (a) HOG-SVM method; (b) LBP-SVM method; (c) GP-SVM method; (d) accuracy comparison curves of four methods