Tunable focus lenses have been developed for decades, yet we find few to none in commercial and consumer applications. On the other aspect, we find tunable lenses well implemented in numerous applications in controlled lab environments, where the closed-loop focal power control, operating conditions, enhanced functionalities, and the footprint area are not primary concerns. The thesis aims to develop tunable lenses with preferences to above concerns. We investigated closed-loop control and reliable operating conditions of two piezo-actuated fluid-membrane lenses, a flexible silicone membrane lens and a stiffer glass membrane lens. Overall, the latter showed superior performance and was less affected by the operating conditions. We further enhanced the functionalities of this glass membrane lens to correct the chromatic aberration and monochromatic aberrations. For the former, we developed tunable doublets by combining two glass membrane lenses filled with different dispersion fluids. For the latter, for tuning the monochromatic aberrations, we segmented the electrode on the actuator of the glass membrane lens to be able to deform the membrane with a non-rotational symmetries. We also developed two unique design approaches for tunable lenses to achieve a high aperture at a least footprint. The tunable lenses investigated and developed in the thesis show promising out-comes to favor implementation in consumer and industrial products.weiterlesen