Can Li, Lü Qimeng, Yingchun Wu, Xuecheng Wu, Xiang Gao, Kefa Cen. Inversion Algorithm of Rainbow Signal Based on Local Minimum[J]. Laser & Optoelectronics Progress, 2021, 58(5): 0529001
- Laser & Optoelectronics Progress
- Vol. 58, Issue 5, 0529001 (2021)
Fig. 1. Optical paths of second-order refracted light p=2 and direct reflected light p=0 around geometrical rainbow angle when a droplet is illuminated by plane wave and their rainbow signals. (a) Optical paths; (b) typical standard rainbow signal of single droplet
Fig. 2. Division of 5 scattering angle regions for second-order refracted light p=2
Fig. 3. Rainbow signals and FFT spectrum of the standard rainbow simulated for a droplet with n=1.33 and D=100 μm. (a) Signals of standard rainbow, Airy rainbow (p=2) and low-pass filtered Airy rainbow; (b) spectrum of the standard rainbow in Fig. 3(a) after FFT processing
Fig. 4. Inversion flowchart of rainbow signal
Fig. 5. Inversion results and error analysis of standard rainbow signals of droplets with different refractive indices (n=1.33, 1.34, 1.35 and 1.36) and droplet sizes (D=30‒150 μm). (a) Absolute error of refractive index; (b) absolute and relative error of droplet size
Fig. 6. Distribution preset inversion results of global rainbow signals of dispersed droplets with different size distributions. (a) Normal distribution; (b) log-normal distribution
Fig. 7. Non-distribution preset inversion results of global rainbow signals of dispersed droplets with different log-normal distributions. （a） μ=60 μm，σ=0.1 μm and μ=100 μm，σ=0.1 μm； （b） μ=80 μm，σ=0.1 μm and μ=120 μm，σ=0.1 μm； （c） μ=40 μm，σ=0.2 μm and μ=80 μm，σ=0.2 μm；（d）μ=60 μm，σ=0.2 μm and μ=100 μm，σ=0.2 μm
Fig. 8. Non-distribution preset inversion results of global rainbow signals of dispersed droplets with different normal distributions. （a） μ=40/60/80/100/120/140/160 μm，σ=2 μm； （b） μ=40/60/80/100/120/140/160 μm，σ=5 μm； （c） μ=60/100/140 μm， σ=10 μm
Fig. 9. Non-distribution preset inversion results of global rainbow signals of dispersed droplets with multi-distributions. (a) Trimodal distribution; (b) binormal distribution
Fig. 10. Experimental results for monodisperse droplets.(a) Standard rainbow image; (b) comparison between experimental standard rainbow signal and fitted signal
Fig. 11. Experimental results for polydisperse droplets. (a) Global rainbow image; (b) comparison between experimental global rainbow signal and fitted signal; (c) non-distribution preset inversion result
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