Design And Fabrication Of Liquid Lens With Inhomogeneous Membrane

Inspired by natural optical system,such as human eyes and cormorant eyes,liquid lens can obtain variable focal length by changing the surface profile,and achieve a large zoom capacity in the small volume.It provides a solution for mobile electronic devices,micro-surgery and other zoom optical system in limited space,so liquid lens have drawn great attention from academia and industry.Recent numerical studies showed that the surface of liquid lens is aspherical,and the surface profile is tunable by changing membranes thickness.However,there are few detailed reports about experimental study on the process of liquid lens deformation.The main reason is that the precise fabrication of inhomogeneous membrane and assembly of a liquid lens with an inhomogeneous membrane have not been solved.On the other hand,it is difficult to measure the aspherical surface profile without contact.In this paper,we implemented the fabrication and dynamic measurement of liquid lens with in homogeneous membrane by solving the abovementioned problems.To numerically analysis liquid lens based on inhomogeneous membrane,2D axisymmetric model was built in finite element analysis software and the non-linear deformation behavior of plano-convex,plano-concave and uniform membrane was systematically studied.In experiment,we fabricated inhomogeneous flexible membranes by spin coating on a curved surface of a pre-machined aluminum mold.An optical coherence tomography(OCT)system was used to dynamically measure the changes of a lens profile without contact.Both simulation and the experiments indicated that conic constant tends to be stable as the curvature of liquid lens increases.The structure of membrane could affect the lens profile in a predictable manner.The membrane thickness was adjusted and conic constant decreased as the increment of the thickness of the membrane increases in the radial direction.To conclude,surface profile of liquid lens can be controlled by designing the membrane structure.For a single liquid lens,the result of ray tracing simulation showed that the liquid lens with a plano-concave membrane(r:25mm)has better optical performance at the same vertex deflection of membranes.The presented study offers guidance for image-quality analysis and optimization of an optical system based on liquid lens.