Study On Liquid Progressive Multifocal Lens Using Elastic Membranes With Non-uniform Thickness

Visual impairment is a non-negligible factor affecting the quality of human life in today's society.Due to the advantages of adjustable focal length,wide field of vision,high detection efficiency,and the ability to take into account both high detection efficiency as well as imaging clarity,the zoom lens has been widely used in the lens industry.At present,the zoom lenses which are popular in the market are mostly mechanical zooming formed by the combination of solid lenses of different focal lengths under certain conditions.The components of them are relatively complicated and expensive.Moreover,zoom lenses are more difficult to focus on progressively than the liquid lens.The liquid lens is simple in a structure which can realize continuous zooming and can adopt electromagnetic,piezoelectric,acoustic wave and other drivers to achieve automatic controllable zooming.Besides,in the research field of liquid lenses,the zooming mode is mostly to adjust the focal length on a single axis and the zooming form is relatively simple.Also,for the elderly with myopia,as the increase of age,the eyes gradually lose the ability to adjust the focal length,not only can not see in the distance,but also the near objects are gradually blurred and require a distance lens to adjust.Therefore,the elderly can apply progressive multifocal lenses under certain environmental conditions.However,the diopter values of far view point and the near view point of progressive multifocal lenses are fixed.The diopter value of the lens needs to adjust and regrind regarding environmental variation but the process is very complicated.Most importantly,it does not only realizes two focal lengths in the upper and lower regions of a lens but also achieves a gradual smooth transition between the diopter distributions as well as the two focal points.Furthermore,the value of the two focal lengths can be adjusted by tuning the liquid pressure in the chamber of the liquid lens.In this paper,a liquid progressive multifocal lens and the mathematical model of the diopter distribution of the lens are proposed and established.And,the target value is confirmed,then the diopter distribution characteristics of the progressive multifocal lens are obtained through calculation.Based on a three-dimensional geometric model of a circular elastic membrane with uniform thickness distribution and various non-uniform thickness distributions,the models are bounded by circular boundary constraints,two parts boundary constraints and three parts boundary constraints.The surface height distribution and corresponding diopter value distribution after deformation of the membrane can be obtained based on the simulation under certain surface pressure conditions.Then the diopter value distribution can be calculated and compared with the designed target value.At the same time,the thickness distribution of the membrane model,the boundary constraints and surface pressure values in the finite element simulation can be continuously adjusted to obtain ideal diopter distribution.The liquid progressive multifocal lens in the paper mainly consists of an elastic membrane of non-uniform thickness distribution,an elastic membrane of uniform thickness distribution,the cavity,transparent support plate,liquid,a capillary channel and boundary constraints.To verify the elastic membrane deformation with diopter distribution and image quality evaluation,especially the non-uniform thickness distribution of the elastic membrane in the lens under certain pressure and constraints,the liquid progressive multifocal lens is simulated in the optical simulation software ZEMAX.Then the deformed membrane after finite element simulation is re-established by reverse engineering method and the three-dimensional materialized model is processed for the distribution of liquid in the lens cavity.Finally,the three-dimensional geometric model of liquid lens and the main optical parameters of the membrane are introduced into the optical simulation software.The optical properties of the membrane are simulated and analyzed under the condition of parallel light source.Experiments have been carried out on liquid progressive multifocal lenses.In the experimental apparatus,the elastic membrane in liquid lens is made of Polydimethylsioxane(PDMS),and PDMS membranes with uniform thickness and non-uniform thickness are manufactured.After the liquid is filled into the lens cavity through the capillary channel,the surface of the lens membrane is deformed under liquid pressure.The laser displacement sensor is used to measure the surface height after deformation and calculate the corresponding diopter distribution.The optical test platform is built and the optical focusing effect of the liquid lens is observed.At the same time,the focal lengths of the lenses are measured and analytical evaluation is made to verify the diopter distribution of the liquid lens.