Study On The Modelling Of Liquid-crystal Micro-optics Structures And Large Aperture Liquid-crystal Lenses Controlled Electrically

Liquid crystal(LC) materials demonstrate a kind of dielectric anisotropy, and currently have been widely used in panel display field and various photoelectric devices. LC lenses controlled electrically have special functions of electrically tuning focal length and swing focus, and are generally presented in an arrayed fashion, and have small optical aperture so as to limit their applications. The technology of the LC lenses with relatively large aperture has become a domestic and international hotspot and thus has attracted more and more attention. The researches about theoretical analysis and experimental techniques of this type of LC device mentioned above are conducted deeply in this dissertation. Firstly, three dimensional modeling about LC director and spatial electrical potential between electrodes of LC device has been done based on the Frank-Oseen continuum elastic theory. To verify the correctness of the modeling, simulations of the classical LC lenses and the new LC lens with focus swing have been done. Finally, based on overcoming the limitation factors of the optical aperture of LC lenses, a layout design of the devices and the corresponding electrode arrangement for realizing large optical aperture have been proposed by combining theoretical calculation and analysis on simulation results. The designed LC lenses with large aperture have been fabricated, tested and estimated. The main works and innovations of the dissertation are as follows:First, three dimensional modeling of LC lenses based on the finite element method has been done, and then the difficulties of numerical computation have been analyzed comprehensively. The discrete trahedron elements with different structures can be transformed to be regular ones by coordinate transformation, which makes the limits of integral expressions the same in the domain and simplify the process of modeling.Then, conventional LC lenses have been simulated and distributions of director and electrical potential have been obtained. Algorithms to simulate point spread functions have been proposed, by which the focal length of lens and the spot size can be obtained. However, the traditional method can only estimate focal length from curvature of phase retardation.Optical performance of LC lens with focus swing controlled electrically has been simulated and analyzed, and disclination lines in it have been discussed. Proposal to suppress disclination lines in LC lens with focus swing to improve the optical performance is provided.Finally, based on the objective to develop LC lens with large aperture, new device structure and patterned electrodes have been designed. Fabrication of the new device, tests upon it and estimation have been completed. To get better performance of ability to converge light, structure of electrodes in four layers and the corresponding patterned electrodes have been designed. Steady electric field in LC layer can be generated in the structure which makes the wavefront of emergent light close to the ideal situation. The aperture of the fabricated LC lens is 2mm and presents the expected ability to converge light, which verifies that the method to design LC lens with large aperture is effective.