Fig. 1. Optical system diagram for laser processing

Fig. 2. Beam expanders commonly used in laser processing. (a) Kepler system; (b) Galileo system

Fig. 3. Schematic of optical system with sequence mode

Fig. 4. Diagram of optical system with non-sequence mode

Fig. 5. Relationship between defocusing amount and distance between beam expanders

Fig. 6. Schematic of tilt angle of beam expander

Fig. 7. Relationship among focal length, defocusing amount and tilt angle of beam expander

Fig. 8. Relationship among peak power, spot diameter and distance between beam expanders

Fig. 9. Relationship among peak power, spot diameter and tilt angle of beam expander

Fig. 10. (a) Distribution of spot energy at different lens distances; (b) distribution of spot energy at different tilt angles; (c) relationship between spot center position and tilt angle of beam expander

Fig. 11. (a) Schematic of experimental setup for measuring focus position; (b) schematic of measuring method; (c) relationship between defocusing amount and lens distance measured in experiment

Fig. 12. Schematic of experimental setup for measuring spot energy distribution

Fig. 13. Distributions of spot energy under different lens distances. (a) Δd=1.0 mm; (b) Δd=0.2 mm; (c) Δd=-0.2 mm; (d) Δd=-1.0 mm