Design and demonstration of DEA-based tunable planar liquid crystal Alvarez lenses

Traditional liquid crystal lenses realize the tunability of focal length by controlling the rotation angle of the liquid crystal molecule. In this paper, a tunable planar liquid crystal Alvarez lenses, which can tune the focal length via the lateral displacement of two planar liquid crystal phase plates actuated by dielectric elastomer actuators (DEA), was designed and fabricated. The maskless laser direct writing technology is employed to fabricate the tunable planar liquid crystal Alvarez lenses. The experiments show that liquid crystal Alvarez lenses achieved a wide varifocal range of 1476 mm ∼ 118 mm with lateral displacement of the two planar liquid crystal phase plates varying from 0.2 mm ∼ 2.5 mm. The proposed varifocal lens has a dynamic response with a rise time of 185 ms and a fall time of 296 ms. Experiments are designed to verify the varifocal capability of the proposed Alvarez lenses, and the experimental results show that it can focus virtual images of an object at different depths in the real environment. The proposed liquid crystal Alvarez lenses have potential applications in compact and miniaturized imaging systems such as camera modules, medical imaging, enhanced displays, etc.