Research On Liquid Crystal Lens Autofocus Technology

As one of the key technologies of digital imaging systems,autofocus is widely used in various imaging fields such as industrial inspection,military aerospace,intelligent surveillance,digital cameras and so on.Its development trend is fast speed,low power consumption,strong stability and miniaturization of the system structure.The dualvoltage-driven liquid crystal lens has the characteristics of electronically controlled focal length,small size structure,low power consumption,etc.,and does not require any mechanical movement and maintains good optical properties throughout the entire focusing range.This topic combines the characteristics of liquid crystal lens devices,and studies the various aspects of the autofocus technology of liquid crystal lens optical imaging system in detail and completes the development and design of the complete autofocus software system.Firstly,the liquid crystal lens optical imaging system is designed.The parameters such as focusing range and field of view of the imaging system are determined.The liquid crystal lens structure used in the imaging system is introduced and tested in detail.Through the research of various image quality evaluation methods,the resolution of optical imaging system and the quality evaluation value of MTF are measured by Imatest software.The experimental results show that the imaging quality of the imaging system is good.Secondly,the liquid crystal lens climbing method autofocus technology is studied.The key research content is the selection of the focus measure function and the focus search algorithm design during the mountain climbing autofocus process.Based on the analysis of several commonly used focus evaluation functions,a new focus evaluation method based on the tenengrad function is proposed.The experimental results show that the method is fast,accurate,and sensitive.Aiming at the characteristics of positive and negative lens for electronically controlled focusing of liquid crystal lens,two kinds of focusing search algorithms are designed.Experiments show that each focusing search algorithm can accurately find the focus position.The applicability and characteristics of the two search algorithms are analyzed in detail.Finally,based on the research of liquid crystal lens autofocus technology theory,the liquid crystal lens autofocus system controlled by PC is designed and implemented.The hardware part of the whole system is mainly composed of liquid crystal lens,CMOS imaging module and voltage driving module.The software system also integrates liquid crystal lens non-polarization imaging module and depth map acquisition module based on the realization of autofocus function.A large number of autofocus experiments are carried out using the software system designed and developed by myself.The experimental results show that the system has good running stability and obvious focusing effect,which provides a productized solution for the practical application of liquid crystal lens imaging system.