Variable-focus Liquid Lens Integrated With A Planar Electromagnetic Actuator

Variable-focus liquid microlens as a new type optical element has been widely used in the modern micro-optics system,biomedical detection and optical communication system.Different from traditional lens varies its focal length rely on adjusting relative position between the lens and the sensor,liquid lens generally by changing its own refractive index or droplet curvature to achieve the zooming purpose.The liquid lenses driven by electromagnetic actuation are the most attractive because of their simple actuating and zooming principle,wide zoom range,and fast response.To deform the shape of optical chamber membrane,an external auxiliary coil is served to provide the driven force,but this type of liquid lens reported before due to the use of external auxiliary coil,makes the lens difficult in plane installation,and unable to realize the integration of the lens body and actuating components,also greatly limits its applications in micro-optics systems.Aiming at the problems of the integration of the lens body and actuating components,we design and fabricate a micro planar electromagnetic actuator,which combined with permanent magnet as power source of the proposed liquid lens.By changing the size of the applied current,the aim of the lens zoom is realized.In this paper,the structure and the zooming principle of the proposed liquid lens was described.According to the basic theory of electromagnetic field,the electromagnetic field distribution of planar coil was studied.Then by analyzing the relationship between applied current and the magnetic force induced between the planar electromagnetic coil and the permanent magnetic,the mathematical model between the lens focal length and the applied current was established.Furthermore,the parameters which may affect the actual zooming performance of the proposed liquid lens were also simulated and optimized.The fabrication process and the key parameters of the lens was studied,we divided the fabrication processinto five steps including planar electromagnetic coil fabrication,SU-8 lens body fabrication,PMMA protective structure fabrication,PDMS membrane preparation and assembly of these four parts.In the testing segment,we set up a test platform,and the performance of this liquid lens is tested from four aspects including surface profiling,optical observation,variation of focal length and dynamic response speed.Lastly,according to the test results,the future improvement and development of this kind of zoom lens are prospected.