Design and analysis of biconvex liquid lens with circular hole plate electrode structure

Abstract

In this paper, based on the research of zoom liquid lens with parallel plate electrode and the principle of dielectrophoresis, a model of the biconvex liquid lens with circular hole plate electrode structure is proposed, which is a novel three-layer liquid lens structure. The dielectrophoretic effect refers to the phenomenon that free dielectric molecules will be polarized and moved by the force in a non-uniform electric field, thus deforming the dielectric liquid. In the dielectrophoretic liquid lens, only two insulating liquid materials with large refractive index difference and dielectric constant difference need to be selected, which can increase the selection range of liquid materials. The liquid lens structure mainly consists of a piece of double-sided conductive flat plate ITO glass with a circular hole and two pieces of single-sided conductive flat plate ITO glass, which respectively form two sets of flat electrode structures to control the upper interface and lower interface of the liquid droplet. In this structure, the influences of the intermediate glass plate on the focus and imaging are reduced by using the flat plate electrode with circular hole. The theoretical analysis of the structure is carried out with simulation software. Firstly, the models of the biconvex liquid lens with circular hole plate electrode under different voltages are built with Comsol software, the data of upper interface and lower interface of the liquid droplet are exported. Then by using Matlab, the surface shapes of the upper interface and lower interface of the droplet are fitted and the corresponding aspheric coefficients are obtained. Finally, the optical models are built with Zemax software, the imaging optical paths and the variation range of focal length under different voltages are analyzed. On the basis of the simulation, the corresponding device is made, and the specific experimental analysis is carried out. The surface patterns of the upper interface and lower interfaces of the droplet of the biconvex liquid lens under different voltages are recorded, the focal length and imaging resolution of the liquid lens are measured. When the operating voltage is in a range of 0–260 V, the focal length varies from 23.8–17.5 mm, which is basically consistent with the simulation results (22.6–15.9 mm). The feasibility of the structure of the biconvex liquid lens with circular hole plate electrode structure is verified experimentally. The imaging resolution can reach 45.255 lp/mm. The results show that this proposed novel three-layer liquid structure of the biconvex liquid lens has the characteristics of simple structure, easy-to-realize and good imaging quality. Therefore, the research of this biconvex liquid lens can provide a new idea for expanding the high-resolution imaging research of liquid lenses and their applications.