Development of liquid crystal adaptive lens with circular electrodes for imaging application

This paper reports the development of the first Liquid Crystal Adaptive Lens (LCAL) with circular electrodes for imaging application. LCAL is an electro-optical device using a set of electrodes to grade the refractive index across its aperture. The principle of liquid crystal adaptive lens is briefly discussed. The special advantages and challenges in using circular electrodes are addressed. Numerical simulation is performed to predict the imaging performance. A prototype of LCAL was designed according to the requirements for application in a microscope imaging system with a diameter of 7.86 mm and a focal length adjustable from 0.2 m to infinity. The structure of the LCAL with circular electrodes includes the top ITO ring electrodes and the connecting wires, insulating layer, ITO plugs, and the bottom ITO conducting wires. This prototype was fabricated on a glass substrate by using micro-fabrication process. The focusing performance of the LCAL with circular electrodes was presented. The experimental results agree well with the simulation results. The imaging experiment of LCAL is performed when LCAL focal length is 1m, 0.38m and 0.2m under incoherent source. The resolution of the images formed by LCAL combined with a fixed lens is indistinguishable from that of the image formed only by a fixed lens, while the contrast is lower.