Recent advances in flexible variable-focus lens

In this paper, the flexible variable-focus lens(FVFLs) is reviewed from two aspects including mechanical variable-focus lenses and electrostrictive variable-focus lenses. The gravity effect and temperature change exist in most FVFLs. Mechanical variable-focus lenses exhibit very large focal length tunability, but their use is limited by their slow response speed. Electrostrictive variable-focus lenses have simple and compact structure, high response speed. Providing a solution for minimizing optical aberrations and maximizing the tunability of focal length or field of view has drawn much attention in recent years. Exploring new driving technology and developing intelligent focus tunable system with low power comsumption will be the main focus of FVFLs in future.