Double liquid-core cylindrical lens utilized to measure liquid diffusion coefficient.

We design and fabricate an aplanatic double liquid-core cylindrical lens (DLCL), which is used to measure the binary liquid diffusion coefficient (D). The front lens of the DLCL is used as both a diffusion cell and a key imaging element; the refractive index (RI) of liquid filled in its core can be measured in the way of spatial resolution. The rear lens of the DLCL is used as an aplanatic component, and either the RI position of spherical aberration (SA) or the SA in a range of RI caused by the front lens can be regulated by selecting the liquid, of which RI is pre-prepared and filled in the rear liquid core. Equipped with the aplanatic DLCL, two methods have been applied to measure the D value of 0.33mol/L KCL aqueous solution at temperature 298.15K. The first method derives D value precisely from the drift rate of diffusion image and the measured D is 1.8508 × 10^-5 cm²/s. Meanwhile, the second method obtains the D value rapidly by analyzing an instantaneous diffusion image and the measured D is 1.8619 × 10^-5 cm²/s. The measured values are in good agreement with the literature value, demonstrating that the designed DLCL works well in measuring liquid diffusion coefficients.