Fig. 1. Schematic diagram of photon number simulation measurement

Fig. 2. Artificial neural network mode of BP

Fig. 3. ANN model training and use

Fig. 4. Relationship between the reflectance of different γ and the radius when μ_s'=4 mm^-1

Fig. 5. Relationship between the relative root mean square and the radius of the reflectance corresponding to different γ

Fig. 6. μ_s'·r as a function of radius r

Fig. 7. Relative error of the true value and predicted value of the reduce scattering coefficient

Fig. 8. Relative error of the true value and predicted value of the γ