Fig. 1. Diagram of experimental facility. (a) Physical device; (b) top view of designed DLCL and image capture display system

Fig. 2. Sums of SA versus refractive index of rear liquid core for KCl diffusion system, the insert is that the SA varies with the refractive index of front liquid core, when the rear liquid core is filled with the best reduced SA liquid n'=1.3974 for KCl diffusion system

Fig. 3. Imaging principle of the DLCL. (a) Imaging with uniform liquid; (b) imaging with two different liquids (n1

Fig. 4. Top view of the imaging of the designed DLCL

Fig. 5. Fitting curve of image width Σi and refractive index ni

Fig. 6. Diffusion images at different moments. (a) 630 s; (b) 1230 s; (c) 1830 s; (d) 2430 s; (e) 3030 s; (f) 3630 s; (g) 4230 s

Fig. 7. Deviation square of concentration for different diffusion coefficients Di