Research On Liquid-crystal Microlens Array With Electrically Tuning And Swing Focus For Wavefront Imaging

In general,the basic requirement for exhibiting the efficiency of imaging observation is to efficiently capture clear target images in complex background environments,which involve two key control elements in the course of light energy flow transportation,that are light intensity or amplitude and wavefront.Due to several factors such as atmospheric turbulence,ambient temperature,and antagonistic means,the wavefronts of target lightwares will generate relatively weak or strong distortion so as to reduce imaging quality.Conventional adaptive optical imaging systems,are usually based on two sets of independent optical paths with core fixed-index and surface profile microlenses and complex mechanical structures to perform wavefront measurement and adjustment operation and thus enhance light intensity imaging capability.The defects including complex structures,large volume,slow response and adjustment,and limited applications,are very apparent.Currently,developing new type of adaptive optical imaging technology with typical characters such as only single optical path,simple control and fast response,already become an urgent requirement and thus receive extensive attention.In this thesis,the liquid-crystal microlens arrays with electrically tuning and swing focus(LCMAETSF),which will be used to enhance the wavefront imaging efficiency through extending dynamic range of wavefront measurement and regulation,are researched based on the controlled electro-optic characteristics of nematic LC materials.The main contents are as follows.Firstly,according to the electro-optical properties of nematic LC materials,a LC microlens architecture driven by a patterned electrode couple is constructed.The spatial distribution behaviors of LC directors are modeled and simulated using the relaxation method and the finite difference method,and further verify the model by constructing a LC microlens array with circular aperture electrode.The layout of key patterned electrodes and structural parameters of the LC microlens arrays are configured through simulations and parameter arrangement acquired before.To measuring and regulating wavefronts in a relatively large dynamic range,two kinds of LCMAETSF with multi-electrode controlled independently to achieve electrically tuning and swing focus,are proposed and then the driving and controlling mechanism is also analyzed carefully.Secondly,metal Al and indium tin oxide(ITO)materials were used to fabricate the LCMAETSFs,respectively.The electron beam evaporation Ni-Au film and the overlaying processes are used to solve the problem that the pins and leads of the ITO external circuit are difficult to be bonded in fusion state.Based on 4?m accuracy requirement,the inductively coupled plasma etching method is utilized to ensure the integrity of the electronic pattern structures.Multi-lead connection between the microlens array and the PCB board is completed by wire bonding technology.Finally,the conventional optical measurements of the LCMAETSFs based on Al and ITO materials,respectively,is conducted by setup an optical testing system suitable for characterizing the tuning and swing focus of the LCMAETSFs developed.The experimental results show that the three-electrode-type demonstrate desired performances of electronically controlled tuning and swing focus in a relatively large range,And the double-layer four-electrode-type LCMAETSFs also demonstrate desired performances of electronically controlled tunable focal length.The loaded mean square voltage signals are also relatively low,so as to more easily measure and adjust wavefronts in a relatively large dynamic range.The above research work already provide a basic technique and key technology support for further developing wavefront imaging means based on more effectively measuring and regulating wavefronts.