Fig. 1. Block diagram of high-speed image measurement system for energy flux density

Fig. 2. Flow chart of photographic system

Fig. 3. Influence of the exposure time on system. (a) Spot image taken at an exposure time of 50 μs; (b) spot image taken at an exposure time of 30 μs; (c) gray value diagram corresponding to Fig. 3(a); (d) gray value diagram corresponding to Fig. 3(b)

Fig. 4. Influence of the lens focal length on system

Fig. 5. Influence of the angle between incident optics and optical axis on system. (a) Spot image taken when the angle between incident optics and optical axis is 30°; (b) spot image taken when the angle between incident optics and optical axis is 40°

Fig. 6. Influence of the lens aperture on system. (a) Spot image taken when the lens aperture is F2; (b) spot image taken when the lens aperture is F4; (c) spot image taken when the lens aperture is F8; (d) spot image taken when the lens aperture is F16

Fig. 7. MLP model

Fig. 8. Fitting curves of the system functionF(Z). (a) Exposure time is 50 μs; (b) exposure time is 30 μs

Fig. 9. Energy flux density distribution of focused spot before and after synthesis. (a) (b) Energy flux density distribution of the focused spot before using the stepwise measurement method; (c) (d) energy flux density distribution of the focused spot obtained by stepwise measurement method