Zoom Imaging System Using Liquid Crystal Lens Array

Zoom imaging system is an optical system in which the focal length is changed within a certain range while keeping the position of the object and image plane unchanged,which can obtain images of different proportions with the same object and image plane.Traditional zoom imaging system is through mechanical movement to change the position of the system components or algorithmic processing to achieve the zoom,the drawbacks of which are the large size of the mechanical structure of the system,the difficulty of the design of non-linear movement,the zoom magnification discrete and image quality degradation.The liquid crystal lens is a new type of lens that can change its focal length only by adjusting the applied voltage,with the advantages of small size,easy integration,and low cost.The use of liquid crystal lens arrays in combination with conventional glass lenses provides a new idea to realize continuous zoom imaging systems without mechanical structures.In this paper,the design and experiments for the combination of liquid crystal lens array and glass lens for zoom imaging system are carried out as follows.First,the design and experiments of a zoom imaging system combining a single liquid crystal lens array and a glass lens are carried out.The principle of the proposed system is explained and theoretically derived,and it is shown that the zoom imaging in the aperture area can be achieved by adjusting the voltage applied to the liquid crystal lens and the position of the glass lens.Subsequently,the structure of the liquid crystal lens array used in the system is explained and tested.The proposed system is also experimentally verified,and the experiments show that the imaging situation of this system is basically consistent with the theoretical derivation,and a zoom ratio of about1:2 can be achieved.Secondly,the design and experiments are conducted for a zoom imaging system combining a positive-negative liquid crystal lens array set with a glass lens.The theoretical derivation and Zemax simulation of the proposed system are carried out to theoretically prove the feasibility of the system.The system is experimentally validated,and it is shown that the system can be used to achieve aperture area zoom imaging with a zoom ratio of about 1:1.5 by adjusting the voltage applied to the liquid crystal lens without mechanical movement of the components,and the resolution of the system can be improved to a certain extent compared with that of a single glass lens.Finally,the design and experiments are carried out for a zoom imaging system combining a negative-positive liquid crystal lens array set with a glass lens.Based on the theoretical derivation and simulation,the proposed system is experimentally constructed.The experiments show that the combined system can achieve zoom imaging without mechanical movement by adjusting the voltage and polarizer orientation only.Moreover,this combined system can improve the resolution,modulation transfer function（MTF）and MTF50 value of single glass lens to some extent.Finally,the similarities of the three types of zoom imaging systems proposed in this thesis are explained,and the differences between the three types of systems are compared in three aspects: mechanical structure,range of system parameters,and imaging conditions.