Fig. 1. Schematic of laser processing system

Fig. 2. Microscopic surface structures of color patch. (a) Yellow patch; (b) orange-red patch; (c) blue patch；(d) amplified blue patch surface

Fig. 3. Elman neural network structure

Fig. 4. Influences of laser frequency and number of laser processing cycles on laser coloring effect

Fig. 5. Influences of laser frequency and scanning speed on laser coloring effect

Fig. 6. Influences of number of laser processing cycles and scanning speed on laser coloring effect

Fig. 7. Flow chart of data processing

Fig. 8. Structures of neural network. (a) net_H; (b) net_S; (c) net_B

Fig. 9. Comparison of actual and predicted hue values

Fig. 10. Comparison of actual and predicted saturation values

Fig. 11. Comparison of actual and predicted brightness values

Fig. 12. Relative error curves of test data

Fig. 13. Predicted laser coloring pattern

Fig. 14. Fabricated laser coloring pattern