Fig. 1. Space-time diffuse reflectance signal measurement scheme for double-layer skin tissue

Fig. 2. Variation curves of diffuse reflection signal with time at each spatial detection position.（a）-（j）Simulation results at SDS of 0.1，0.2，0.3，…，1.0 cm，respectively

Fig. 3. Convolutional neural network inversion model

Fig. 4. Training and testing of convolutional neural network inversion model

Fig. 5. Inversion results of optical properties of double-layer tissue (μ_a1, μ_a2, and μ_s)