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

Design of spherical aberration free liquid-filled cylindrical zoom lenses over a wide focal length range based on ZEMAX

A systematic design idea for liquid-filled cylindrical zoom lenses with ideal imaging quality over a wide focal length range is introduced in detail. The PWC method is used to calculate the initial structure parameters of the zoom lenses, and the optical design software ZEMAX is used to eliminate the spherical aberration at different focal lengths. Lenses named SLCL-Doublet are finally designed, which are formed by a symmetric liquid-core cylindrical lens (SLCL) filled with variable refractive index (RI) liquid and a doublet cylindrical lens capable of significantly weakening the spherical aberration. The focal length of the SLCL-Doublet continuously decreases from 101.406 mm to 54.162 mm as the liquid RI changes from 1.3300 to 1.5000. Calculated over 75% of the full aperture, the root mean square (RMS) spot radius of the SLCL-Doublet is always less than 7 µm over the whole focal length range, and the peak-to-valley wavefront error remains below the λ/4 limit when the focal length ranges from 62.373 mm to 65.814 mm, within which the lenses approach the diffraction limit, demonstrating improvement in the optical performance over that of previously designed liquid-core cylindrical lenses. The sources of potential fabrication and installation errors in the practical implementation of the SLCL-Doublet are also analyzed in detail. The SLCL-Doublet is demonstrated to be characterized by high imaging quality and easy installation, which enriches the types of core optical element for measuring the liquid RI and liquid diffusion coefficient and provides guarantee for improving the measurement accuracy.

Measuring the mutual diffusion coefficient of heavy water in normal water using a double liquid-core cylindrical lens

The mutual diffusion coefficient of heavy water in normal water is measured over a temperature range of 20 to 40 °C using a novel method called the shift of equivalent refractive index slice (SERIS). The measured values range from 1.9086 × 10⁻⁵ to 3.0860 × 10⁻⁵ cm²/s and fit the Arrhenius equation well, and the calculated data from the equation are consistent with the literature values obtained by the interference method. The SERIS method is based on a double liquid-core cylindrical lens (DLCL); the front liquid core of the DLCL is used as both a liquid diffusion cell and a key imaging lens, and the resolvable minimum of liquid refractive index is δn = 6.15 × 10⁻⁵. The rear liquid core is used as an aplanatic lens, and the transversal spherical aberration is less than 1 μm. The SERIS method provides a new way to measure mutual diffusion coefficients of liquid and has the following advantages: visual measurement, use of a simplified device, and easy operation.