The Research On Fabrication And Application Of Plane Lens And Polarization Grating Based On Liquid Crystal

Liquid crystal is widely used in modern life.The geometric phase element made of liquid crystal has attracted the attention of researchers because of its convenient manufacture and low cost,such as plane lens and polarization grating made of liquid crystal material.In this paper,the preparation method and principle of planar lens based on liquid crystal materials are studied.The optical edge of the object is detected by the liquid crystal polarization grating and the liquid crystal plane lens.The results obtained in this thesis dissertation are as follows:Three methods of preparing liquid crystal plane lens are proposed.Polarization holographic exposure and projection exposure based on DMD can prepare traditional liquid crystal plane lens,and duplicate exposure can prepare super large F/# plane lens.Among them,the polarization holographic exposure method can easily produce large size and small focal length plane lens samples.When the projection exposure method based on DMD is exposed,it is less affected by the environment,and the fringes of the exposed samples are regular.The method of duplicating exposure has the advantages of simple light path,high exposure efficiency.It can expose plane lens with an F/# of 9472.4 and polarization gratings with a period of 2.2mm.It provides a new idea for the fabrication of super large F/# plane lens and super large periodic polarization grating.The one-dimensional optical edge detection of the object is realized by using the liquid crystal polarization grating.It is proved that when two liquid crystal polarizing gratings are placed in parallel,the diffraction angle of the beam passing through them can be changed by rotating the relative angle between the two liquid crystal polarizing gratings,so as to adjust the resolution of optical edge detection.Under the conditions of 635 nm,532nm and 450 nm incident light,the edge information of the object can be extracted well.The other light spots produced by the polarization grating,except for the ± 1 level light spot,have no effect on the edge detection results.The wide spectrum applicability of optical edge detection of liquid crystal polarization grating is verified.It can provide powerful help for parallel and super large image data processing.The two-dimensional optical edge detection of an object is realized by using a liquid crystal plane lens.It is found that the liquid crystal plane lens can detect the optical edge of the object at various wavelengths,which shows that the liquid crystal plane lens has wide-spectrum applicability.Compared with the liquid crystal polarization grating,the two-dimensional edge detection based on the liquid crystal plane lens completely retains the edge information without blurring.The influence of the exposure time of CCD sensor on edge detection is studied.When the exposure time is about 0.2-0.4s,the effect of edge detection is better.When the exposure time is about 0.3s,the exposure time is 0.3s.Low cost,easy mass production and two-dimensional detection mode make the practical application of the edge detection mechanism possible.Moreover,the properties of the film can also play a great role in the field of flexible electronics.