Fig. 1. Schematic of speckles

Fig. 2. Schematic of experimental optical path

Fig. 3. Distribution of light spots caused by different placement of attenuators. (a) Experiment 1; (b) experiment 2; (c) experiment 3

Fig. 4. Optical path of a single attenuator

Fig. 5. Analysis of overlap between primary spot and first grade spot

Fig. 6. Optical path for attenuators showing V-shape

Fig. 7. Optical path for parallel attenuators

Fig. 8. When d reaches the maximum value, the incidence angle varies with the relative refractive index

Fig. 9. Change curve of spot center spacing with incident angle in GaF₂ medium

Fig. 10. Change curve of spot center spacing with incident angle in K9 glass medium

Fig. 11. Change curve of spot center spacing with attenuator thickness in GaF₂ medium

Fig. 12. Change curve of spot center spacing with attenuator thickness in K9 glass medium

Fig. 13. Main spot without speckles

Fig. 14. Placement method 1 and amplification of some details

Fig. 15. Placement method 2 and amplification of some details

Fig. 16. Two groups of attenuators are placed in a double parallel symmetric structure