In order to study an aspherical liquid lens with simple structure and easy realization, an aspherical double-liquid lens based on planar electrode is designed based on the dielectrophoretic effect. The droplet in the dielectric electrophoretic liquid lens is polarized in the electric field and moves towards the higher electric field strength under the action of the dielectrophoresis force. With the change of the applied voltage, the dielectrophoresis force also changes, thus the contact angle of the droplet at the solid-liquid interface changes. Firstly, the models of the aspherical double-liquid lens under different voltages are established with Comsol software, and the interfacial profile data are obtained. Then the aspherical coefficients and the surface type of the fitted interface are obtained with Matlab software. Finally, the corresponding optical model of double-liquid lens is established with Zemax software. The variable range of focal lengths and root mean square (RMS) radii of the aspherical double-liquid lens at different voltages are obtained. In order to further study the characteristics of the aspherical double-liquid lens, it is compared with a spherical double-liquid lens model. Based on the contact angle theory of liquid lens and Gaussian optics theory, the relationship between the interfacial curvature radius of the spherical liquid lens and the applied voltage, and the relationship between the focal length and the applied voltage are obtained, respectively. The liquid material, cavity structure and droplet are the same as those of the aspherical lens. The corresponding spherical double-liquid lens model is established according to the two expressions relating to Zemax, and the voltage value is the same as that of the aspherical lens. Thus, the variable ranges of focal length and RMS radius in the spot diagram of the spherical double-liquid lenses at different voltages are obtained. Then, they are compared with those of aspherical double-liquid lens, and the results show that the variable range of focal length of the aspherical double-liquid lens is larger than that of the spherical double-liquid lens, and the imaging quality of the former is better than that of the latter. Moreover, through the device fabrication and preliminary experimental analysis of the aspherical double-liquid lens, the imaging resolution can reach 40.318 lp/mm. The aspherical double-liquid lens proposed in this work has the characteristics of simple structure and easy realization, which can provide a new scheme for high-quality imaging of liquid lens and its applications, and can expand the application scope of liquid lens.
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.
According to the principle of dielectrophoresis, an aspherical double-liquid lens based on parallel plate electrodes is designed. In comparison with the liquid lenses based on patterned-electrodes, the aspherical double-liquid lens structure uses continuous electrodes, which have the advantages of simpler processing, lower cost, easier realization and more practicability. The droplet in the dielectric electrophoretic liquid lens is polarized in the electric field and moves towards the higher electric field intensity under the action of the dielectrophoretic force. With the change of applied voltage, the dielectrophoretic force varies, thus the contact angle of the droplet at the liquid-liquid interface is changed. Firstly, the models of aspherical double-liquid lenses under different voltages are established with Comsol software, and the data of interfacial profile are derived. Then using Matlab software, the derived interface surface data are fitted by polynomial, and the aspherical coefficients are obtained. Finally, the optical models are built with Zemax software, and the variation range of focal length and root mean square (RMS) radius of aspherical double-liquid lens under different voltages are analyzed. In order to further study the characteristics of aspherical double-liquid lens, it is compared with spherical double-liquid lens model. The liquid material, cavity structure and droplet volume of spherical double-liquid lens are consistent with those of aspherical double-liquid lens. The corresponding spherical double-liquid lens model is established by using the Zemax software, the range of focal length and RMS radius of spherical double-liquid lens under different voltages are obtained. The results show that the focal length variation range of aspherical double-liquid lens is larger than that of spherical double-liquid lens, and the imaging quality of the former is better than that of the latter. The experimental preparation of the designed aspherical double-liquid lens device is carried out, and its focal length and imaging resolution are measured. When the operating voltage is in a range of 0–280 V, the focal length varies from 54.2391 to 34.5855 mm, which is basically consistent with the simulation result. The feasibility of the liquid lens structure is verified experimentally. The imaging resolution can reach 45.255 lp/mm. The designed aspherical double-liquid lens based on the parallel plate electrode can provide a new scheme for the high-quality imaging of liquid lens and its application, and can expand the application scope of liquid lens.
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